Our messed-up relationship with food has a long history. It started with butter.

Have you ever eaten butter by the spoon? Butter without toast to prop it up or eggs to fry in it - butter for its own tangy, full-flavored, exquisite sake?

Elaine Khosrova does this, not infrequently. She warms a variety of types to room temperature, gets a glass of water to clear her palate between rounds and pries delicately at her subjects with scientific curiosity, observing how the different textures yield to her knife. Seven types of butter are in front of her today, made from cow, sheep and goat cream, ranging from a sunny gold to a soft, bridal white.

"You see how totally cohesive this is?" she says, prying at the first and mildest sample, a sweet cow butter made in New Zealand by a brand called Anchor. She slides a slab of the thick, pale yellow Anchor onto her spoon.

The author of "Butter: A Rich History," Khosrova has worked as a pastry chef, at a restaurant trade journal, in a magazine test kitchen and as the editor of a cheese magazine, and she has researched the history of butter going back to the Stone Age. The resident of Hudson Valley, New York, has made it her job to know the differences between conventional and grass-fed, between sweet and cultured (fermented with live cultures). She can explain how tender springtime grass creates butter that's more yellow (it's from the beta carotene in the plants), and, when she's tasting, pick out the diacetyl (that quintessential buttery flavor) and the lactones (they impart a sweetness, she says). She is, in short, a butter savant in a country coming around to butter again.

"It's been downtrodden for so long, between the margarine wars and the diet wars," says Khosrova. Even in the '80s, when "fat was so taboo," she says, "I never gave up on butter."

How, precisely, do you taste-test butter? It turns out it's much like tasting wine, only ... thicker. Khosrova lifts the spoon, sniffs and slides it into her mouth, the spoon clanking against her teeth.

"I try to kind of keep it in the front of my mouth," she says stickily. "You really want it to dissolve as slowly as possible." She makes a breathy, guttural sound. "You're trying to almost smell from the back of your throat."

Between the initial saltiness and the full-flavored fattiness that coats the tongue and makes everything else seem like a distant dream, Khosrova's palate catches the butter's "terroir." It has "almost, like, a green vegetable quality," she says. "It's so fleeting. It's there and then it's gone."

The amateur tries to catch this subtlety and just winds up with a mouthful of butter. Which is not actually a bad thing.

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Khosrova's book, which was released in November, could not have better timing. In recent years, countless headlines have declared butter "back," amid some science suggesting we may have overrated its health dangers. People are putting butter in their coffee, and the demand for "real food" is pervasive enough that in 2015, McDonald's swapped out margarine for butter in its Egg McMuffin.

Butter's story is a very American story, because the arc of its vilification and subsequent redemption is a parable for how we get food wrong time and again. We alternately demonize and idealize individual ingredients - not just butter but also sugar, caffeine, red wine and supposed miracle foods featured on "The Dr. Oz Show" - and in doing so, we miss the big picture. Even now, at butter's supposed moment of glory, many nutritional scientists worry that the pendulum may be swinging too far in its direction. American food trends are hopelessly reminiscent of Newton's third law, says David L. Katz, founding director of the Yale-Griffin Prevention Research Center: "For every boneheaded action, there's an opposite and equally boneheaded reaction."

But before we get to all that, it helps to go back to the beginning. Khosrova writes that butter is believed to hark back to the Neolithic era. While the exact circumstances of its discovery are unknown, she imagines a herdsman storing milk inside an animal skin. Over the course of many hours, the milk is ripened by bacteria, chilled and agitated by a bumpy ride, causing delicious, golden butter flakes to form, and delighting the herdsman.

Over time, Khosrova says, butter became not just beloved but revered. In ancient Sumeria, people brought butter offerings to a temple to celebrate the union of a fertility goddess with a mythological dairy shepherd. The Vedic Aryans filled their sacred texts with references to butter ("waves of butter flow like gazelles before the hunter," went one hymn), while Tibetan Buddhist monks made sacred butter sculptures for centuries, and still do. Ancient Druids paid homage to a pagan goddess by making butter - "the phallic thrusting of the dasher in the churn" symbolizing "the blessing of fertility," she says. Khosrova says butter was seen as holy by many people in part because they didn't understand how it formed. If things like temperature or fat content weren't right, butter wouldn't emerge at all. Its appearance, therefore, was capricious and special - proof of the goodness of the universe.

"It was really valuable, too," Khosrova says. She is tall and willowy; friendly with a touch of reserve. When she talks dairy, she is scrupulous, sometimes consulting a trade manual that deals with matters such as oxidation and rancidity. "It tasted delicious, it was used as a medicine, it was used for waterproofing." And "it was rich. If you didn't have a lot of animal meat, for instance, you had this richness to sustain you."

By the 16th century, buttermaking was well established as women's domain, but it eventually went male and mechanical during the Industrial Revolution, marked by inventions such as the centrifugal cream separator, and the rise of commercial creameries with big equipment that was believed to require muscly men. By 1887, the annual report of the Nebraska Dairymen's Association was bidding a florid goodbye to the "sound dairymaid," with her "full, rounded arm" and "sweet voice." Not too long after that, butter began its decline.

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The story of butter's shifting fortunes over the past century is complex and messy, featuring a sharp-elbowed war between butter and margarine, changing scientific wisdom over matters such as saturated fat and trans fats, and finger-pointing over an obesity epidemic that has panicked policymakers, advocacy groups and average Americans.

Once upon a time, Americans ate butter unapologetically. In the early 1900s, we consumed more than 18 pounds of butter per person per year, according to data from the U.S. Department of Agriculture. Margarine, invented in 1869 and cheaper than butter, was attacked early on by the dairy industry and subjected to all sorts of regulations. But margarine's fortunes rose over time, assisted by scarce butter supplies during World War II and concerns over the saturated fat in butter, and it surpassed butter in popularity during the 1950s.

More recently, as the health impact of artificial trans fats prevalent in some forms of margarine have come to light, as our interest in more "natural" products has grown, and as sugar has taken its place as the most hated of foodstuffs, butter has come to be revered in many circles, like a long-lost love back from war. Butter consumption surpassed margarine's in 2005, and as of 2014, the average American was consuming 5.6 pounds per year - a 40-year high, though nowhere near where it once was.

In her book, Khosrova writes about the benefits of certain micronutrients in butter, especially the grass-fed kind. And in recent years, research has prompted debates over just how saturated fats affect the body. But many nutritional experts say butter is, at best, a neutral force in the diet and recommend moderation; if we went overboard in demonizing it, neither should we lionize it. "The type of fat we eat is very important, and an optimally healthy diet will be low in butter," emails Harvard doctor and nutritionist Walter Willett. "The central reason for confusion is the issue of to what butter is being compared."

Willett says butter is clearly not as healthful as certain kinds of oil, such as olive, soybean and canola. But on the other hand, replacing butter with carbohydrates doesn't constitute an improvement as far as risk of cardiovascular disease. In other words, if you cut back on butter, sub in olive oil, rather than low-fat cookies.

Katz, of the Yale-Griffin Prevention Research Center, says the butter-is-back story line reflects our failure to look at our own diets as a whole.

"We seem to be in a cycle lasting decades of seeking sequential scapegoats. Right now there's a cottage industry in implying that the one thing wrong with our diets is sugar ... That doesn't exonerate pepperoni pizza," Katz says. "The focus on a scapegoat invites the food industry to do what they've done to us for decades, and that is keep inventing new kinds of junk food."

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Khosrova is a fan of moderation when it comes to butter, if only because her beloved condiment is packed with calories and so flavorful that a little goes a long way. But on tasting days, moderation is by necessity on hold.

The seven butters on display come from six countries - France, New Zealand, Ireland, Canada, England and two from the United States - the priciest being the $24 sheep butter by Haverton Hill Creamery in California which arrives in what looks like a small ice cream tub. All are salted to make comparisons easier.

Over time, even the amateur starts to pick up on the subtleties. There's a butter from Stirling Creamery in Ontario made from whey cream (a byproduct of the cheese-making process), which has what Khosrova calls an "umami cheesiness" that does a back flip in your mouth. There's a cultured butter from Vermont Creamery that's a startling 86 percent butterfat, rather than the 80 percent of most of the others - it's at once milky and tangy. The French cultured butter from Isigny Ste-Mere, churned in a traditional style, has a wonderful balance, the tanginess mixed with coarse rock salt and a satisfying fatty fullness at the end. Separate from the tasting, Khosrova pulls out a butter-that-shall-not-be-named as an example of what can go wrong; its flavor is marked by a distinct cardboardiness, which she says is likely related to compounds known as aldehydes.

There is so much to know about butter, such as how cows convert plant matter into fatty milk, and why some breeds make better-tasting butter, and what precise combination of elements makes Land O'Lakes taste, Khosrova says, "like my childhood." For "Butter," Khosrova traveled to Bhutan, Ireland, Wisconsin and Iowa; she talked to an animal science expert and an expert in lactation physiology. Abundant milk-producing Holsteins are popular in the dairy world, Khosrova says, but when she makes her own butter, which is often, she uses Jersey cream she gets from a shop about 20 minutes from her home in New York's Hudson Valley. (However, the gold standard, in her opinion, is the "fabulous cream" of Guernsey cows, which is "really hard to find.")

Unlike Khosrova, the amateur unused to eating so much butter at once finds herself slightly queasy four butters in, and a little punchy. (This makes it, again, not unlike a wine tasting.) But she rallies at the end for the pricey sheep butter, which tastes for all the world like the strip of fat you pull off lamb chops, and for a goat butter by Delamere, which is sweet and gamy and somehow - this is hard to describe - tender. It nearly brings tears to the eyes.

"That's so funny," says Khosrova. "Michael Pollan wrote about a butter that he tasted in Spain and he said it was absolutely 'poignant.' That was the word he used."

Another amateur at the tasting asks what the goat butter would pair well with, but the answer is already obvious. Clearly, a spoon.

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Cultured Butter

24 tablespoons (makes about 12 ounces)

"Churning" your own butter via a food processor is surprisingly easy; culturing it means introducing a fermenting/acidifying agent that will make the end result richer-tasting and somewhat easier to spread at a cool temperature. Baking experts say it helps produce a more tender crumb.

During the 12 to 24 hours' chilling time, the cream will be tempering, or, as "Butter" author Elaine Khosrova describes it, changing "the crystalline structure of its fats." The buttery flavor and acidity also intensifies a bit more, she says.

Do not knead the final mass of butter on a wooden surface, to avoid picking up any residual odors. If you choose to add salt, keep in mind that 8 tablespoons of commercial salted butter contains about 1/4 teaspoon fine salt.

You'll need an instant-read thermometer and cheesecloth.

We used a small amount of real buttermilk to act as the culturing agent in testing; cultures for making butter and buttermilk are available online via www.cheesemaking.com (New England Cheesemaking Supply).

MAKE AHEAD: The cream-culture mixture needs to rest at room temperature for 16 to 24 hours, then be refrigerated for 12 to 24 hours before processing/churning. For best flavor, the cultured butter can be refrigerated in an airtight container for up to 1 month, or frozen for up to 4 months.

Adapted from Khosrova's "Butter: A Rich History" (Algonquin Books, 2016).

Ingredients

1/8 teaspoon freeze-dried Flora Danica culture, buttermilk culture (may substitute 1/3 cup creme fraiche or regular buttermilk; see headnote)

4 cups heavy cream, preferably not ultrapasteurized

Kosher salt (optional)

Steps

Combine the culture and 1 tablespoon of the cream in a food processor. Let the culture defrost for a few minutes and then work it into the cream so it's grainy. (If you're using creme fraiche, mix it well with 1/4 cup of the cream.)

Heat the remaining cream to 75 degrees in a saucepan on the stove top (low heat), then add it to the food processor; pulse until well incorporated. Transfer the mixture to a bowl, cover loosely with plastic wrap and let sit for 16 to 24 hours, during which time it will thicken a bit, like creme fraiche or sour cream. Then cover and refrigerate for 12 to 24 hours.

Just before you return the mixture to the food processor for "churning," heat the chilled mixture to about 55 degrees by seating its bowl in a larger bowl that's filled with warm water, stirring gently all the while; this should only take a few minutes.

Transfer the mixture to the food processor; puree for 5 to 8 minutes, during which time the mixture will thicken further and change color from off-white to pale yellow. (Once it starts to look pebbly, it's almost butter.)

After another minute, the cream will look curdled and suddenly separate into a milky liquid and small curds of yellow butter. Transfer to a fine-mesh strainer and drain the liquid (reserve it, if you wish; some folks use it for baking bread and watering plants). Rinse the mass of butter curds briefly under cool water, to harden them a bit and get rid of further milky residue.

Wrap the butter in a few layers of clean, slightly damp cheesecloth, then place it in a clean bowl or on a non-wooden surface (preferably marble). Knead vigorously with your hands, or slap the hunk of butter against the surface repeatedly until the butter feels creamy and dense, about 3 minutes, stopping to unwrap and work in a little salt, if desired.

The butter can be served right away, or molded or pressed into a shape before you store it.

Nutrition | Per tablespoon: 110 calories, 0 g protein, 0 g carbohydrates, 12 g fat, 7 g saturated fat, 30 mg cholesterol, 0 mg sodium, 0 g dietary fiber, 0 g sugar