Science vs. chef’s intuition: In search of the perfect cacio e pepe

Cacio e pepe, in its traditional form, consists of exactly five ingredients: pasta, pecorino Romano cheese, black pepper, salt and water. With such a short list, you might think it would be a cinch to prepare. But as anyone who has tried to make this iteration of the classic Roman dish will attest, that couldn’t be further from the truth.

The difficulty lies in creating a perfect emulsion of cheese and starchy pasta water to form a luscious, silky sauce to coat the spaghetti — not the clumpy, broken mess that happens when conditions are less than ideal.

How do you achieve cacio e pepe perfection? Turn to science. Or so I thought.

In April, eight researchers from the University of Barcelona, the Max Planck Institute for the Physics of Complex Systems in Germany, the University of Padova in Italy, and the Institute of Science and Technology Austria published a paper that promised to crack the code to the notoriously finicky pasta recipe. In the paper, titled “Phase Behavior of Cacio e Pepe Sauce” and published in Physics of Fluids, they wrote that the keys to success come down to starch and heat.

“The team first focused on the starch in the pasta water as the key ingredient for a perfect sauce. Typically, fatty substances like cheese cannot mix with water, but a stabilizer like starch helps to bridge that gap,” they shared in a news release. “The other key element of a perfect cacio e pepe sauce is heat — or rather, a lack of it. Too much heat denatures the proteins inside the cheese, causing them to stick together and leading to the dreaded clumps.”

To address these issues, the researchers suggest starting with a starch gel (heating water with potato starch or cornstarch) to control the starch levels instead of relying on the ambiguous amount that remains in pasta cooking water. This gel is blended with pecorino Romano and additional water before the pepper is added, then that mixture is gradually heated before being combined with the cooked pasta. Reserved cooking water is then added until the desired consistency is reached.

I love science, so the promise of cacio e pepe perfection sent me right into the kitchen. I was excited to give it the old college try to test whether the researchers’ method was worthy of sharing here, but unfortunately, the recipe isn’t one I’d recommend for home cooks — and it even threw this food professional for a loop.

Making the starch gel was fairly straightforward. I combined cornstarch with water and nuked it in the microwave until it thickened and became translucent. Next, I added it to a blender along with the cheese and more water and blended until smooth before adding the black pepper. I scraped the cheese sauce (more like a paste, in my opinion) as best I could into a pan. In a misreading of the instructions (they weren’t very clear), I combined the cooked pasta (that you can let cool for up to 1 minute “to prevent the excessive heat from destabilizing the sauce”) with the sauce to heat it up together (instead of heating the sauce on its own first, as directed).

The first issue I encountered was trying to gradually heat the sauce on the stovetop. Medium on our office kitchen’s induction cooktop proved too high, as clumps quickly formed. Only later did I realize that the researchers used a sous vide machine in their experiment to slowly increase the temperature over 40 minutes. They readily admit this is impractical in a home kitchen.

And then there was the pasta-to-cheese ratio: 300 grams of pasta, 200 grams of cheese. I love cheese as much as the next person, but this was way too much for my tastes. The result was a gloopy, overpowering mess of pasta. Sure, I could have used less cheese and tried a gentler heat, but even still, calling for a starch gel, a blender and precise monitoring of heat over an extended period was too much for a recipe that’s meant to be simple and quick.

I decided to pivot.

The researchers cited a YouTube video with Italian chef Luciano Monosilio as the source of the starch gel idea. But before he gets there, Monosilio demonstrates a more practical method: Remove some of the pasta cooking water after just a few minutes, giving it more time to cool down while the spaghetti continues to cook; combine the grated cheese with pepper and some of this cooler pasta cooking water in a new, cold skillet before adding the al dente pasta; and then slowly warm it, adding more of the cooled (but still warm) reserved pasta cooking water as needed. Taking my lesson from the previous trial, I decreased the amount of cheese (2½ ounces, or 71 grams, for 8 ounces, or 227 grams, of pasta) and decreased the heat used for warming it up (medium-low instead of medium).

I did my best at guessing when to pull some of the pasta water and how much to add at each instance. Based on my own culinary intuition, I was able to achieve success! But then, when I tried to re-create that beautiful bowl of cheese and noodles with exact measurements so I could write down the recipe, it didn’t come together as it had just moments before.

My next attempts were even more frustrating. I tried out a few methods I found in cookbooks and online in a quest to do as the Roman traditionalists say and stick with those five ingredients: pasta, its cooking water, pecorino, pepper and salt. None of them worked.

Over two days, I went through about six iterations, more than three pounds of dried spaghetti and more wedges of cheese than I care to admit.

I was lost in a carb- and cheese-induced haze and needed help. So I reached out to chef Matt Adler of Caruso’s Grocery and Cucina Morini, both in Washington D.C., and asked him to be my guide. I told him about the research paper, and in preparation for our meeting, he also tried to prepare cacio e pepe the traditional way.

“My first one was like scrambled eggs,” he told me when I visited him at Cucina Morini one afternoon. Of the 10 attempts he made, he was happy with only one of them. “Why can’t I get this?” As with me, frustration set in, and he went home to do more research.

“I went into this saying I’m going to make this recipe with no butter. That’s how they say every restaurant does it in Rome,” Adler said, but he found that fat is the key to cacio e pepe sauce success. “We emulsify sauces using butter all the time.”

Adler starts by boiling the pasta in lightly salted water. “Less salt than I would put in normally, but we use a lot of the water.” The type of dry pasta also matters. “Bronze cut is such a must for this,” he said, noting how the rough exterior helps with creating a smooth sauce to cling to the spaghetti.

Meanwhile, he blooms freshly cracked peppercorns in a combination of olive oil and butter. It’s important to coarsely grind your own pepper for the best flavor, Adler said. And while toasting spices in a dry skillet does enhance flavor generally, he prefers heating the pepper in fat to better infuse its flavor throughout the dish. When the pasta is almost done, it joins the bloomed peppercorns in fat to continue cooking with some of the pasta water, then more butter is added to the pan. The pan is moved off the heat, then it’s time to add the cheese.

“Sometimes pecorino is a little too barnyard-y, too funky,” Adler said, which is why he prefers to combine it in equal parts with Parmigiano-Reggiano, grana padano or any other Parmesan-like cheese for a tamer flavor. Avoid pre-grated cheeses and their added starch coating, and instead grate the cheese yourself as finely as possible to aid in the emulsification of the sauce. One might be inclined to reach for a Microplane, but neither Adler nor I had much luck. Instead, opt for the small, starlike spikes on your box grater, which are specifically designed for finely grating hard cheeses. (You’re not alone — I’d never used that side of my box grater either.)

The grated cheese gets added a bit at time. I watched Adler as he repeatedly tossed the pasta in a deep, heavy-bottomed skillet — noodles and sauce shooting up into the air before folding back onto themselves. Wait to add the next sprinkle of cheese until the first has been incorporated. (For cooks who aren’t able to perform such pasta acrobatics, similar results can be achieved by leaving the pan on the stovetop and shaking it back and forth with one hand while vigorously stirring with the other.) “I think agitation here is important,” Adler said; it helps release even more starch to better aid in emulsification.

Adler then returned the pan to the flame and added more pasta water to give it a saucier consistency than some other recipes suggest — and I watched as bubbles appeared, just barely reaching a simmer, but the sauce remained smooth and luscious even at such a high temperature. “If you were to boil it, it would separate at some point,” he warned, but the fat allows for some leeway with heat and for you to get everything hot ahead of serving.

The result is a cheesy, saucy, peppery pasta that can stand up to the minute or two it takes to plate, garnished with more cheese and pepper. “Half of those YouTube videos with those Italian guys, it didn’t look that great. The sauce didn’t look like that,” Adler said, referring to the picture-perfect pasta before us, “and that’s what I want.”

With a delicious demo now in my back pocket and license to break from tradition by adding some fat to the mix, I returned to our office kitchen to give it a go on my own. When it came time to add the cheese to the pan, scars from my previous attempts filled me with anxiety, but my fears slowly slipped away with each addition as I watched the grated crumbles become one with the rest of the ingredients in the skillet. Huzzah! Victory at last.

When I looked back at the research paper news release, I noticed a mention of pasta alla gricia, which is cacio e pepe plus guanciale. “This recipe seems to be easier to perform, and we don’t know exactly why,” researcher Daniel Maria Busiello said in the press release. Well, I’d bet my life savings that the answer to that is fat: specifically, the rendered fat from the cured pork cheek.

“It’s not like we’re adding anything crazy,” Adler said of his far-less-fussy olive-oil- and butter-laden cacio e pepe. “Those freaking Romans, always talking their smack about not using any butter.”

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Cacio e Pepe (Spaghetti With Cheese and Black Pepper)

12 cups water

1 tablespoon fine salt

8 ounces dried bronze-cut spaghetti

1½ tablespoons extra-virgin olive oil

6 tablespoons unsalted butter, divided

1 teaspoon freshly cracked black pepper, plus more for serving

1½ ounces Parmesan cheese, very finely grated (½ cup), plus more for serving*

1½ ounces pecorino Romano cheese, very finely grated (½ cup), plus more for serving*

Add the water to a large pot, set over high heat and bring to a rolling boil. Add the salt, followed by the pasta, and cook, stirring occasionally, until just shy of al dente, about 2 minutes less than the package instructions.

Meanwhile, in a medium (10-inch), preferably deep, skillet or sauté pan over medium-high heat, heat the oil and melt 2 tablespoons of the butter. Add the pepper and cook, stirring frequently, until fragrant, 30 to 60 seconds. Remove from the heat and set aside until the pasta is ready.

Once the pasta is ready, return the skillet or sauté pan to medium-high heat. Use tongs to transfer the pasta from the pot to the skillet, add 1 cup of the pasta cooking water, and cook, stirring frequently, until the liquid reduces by around half, about 3 minutes. Add the remaining 4 tablespoons of butter and continue cooking, stirring constantly, until the butter melts and the pasta is evenly coated, about 1 minute. Remove from the heat.

Working in four batches, add one-quarter of both cheeses and stir vigorously until it’s melted and thoroughly combined. Repeat with the remaining cheese.

Return the skillet to medium-high heat, add ¼ cup more of the pasta cooking water, and cook, stirring constantly, until hot, 1 to 2 minutes. (Don’t let it get hotter than a bare simmer or you risk breaking the sauce.) Remove from the heat, divide among bowls and serve immediately, with more cheese and pepper sprinkled on top.

Substitutions: For spaghetti, use any long pasta shape. For dried pasta, use fresh pasta. Instead of the Parmesan and pecorino, use just one or the other.

*Notes: Do not use pre-grated cheese that includes anti-caking agents, which can result in a grainy sauce. Grate your own cheese as finely as possible, such as with the star-shaped spikes on a box grater. Storage: This dish is best as soon as it’s made.

2 to 3 servings (makes about 4 cups).

Nutrition per serving (1⅓ cups), based on 3: 638 calories, 57g carbohydrates, 70mg cholesterol, 38g fat, 3g fiber, 18g protein, 20g saturated fat, 621mg sodium, 3g sugar

— Adapted from chef Matt Adler of Cucina Morini and Caruso’s Grocery