Don’t toss your broccoli and cauliflower scraps; make this cheesy soup

All the cruciferous bouquets are streaming into my kitchen: cauliflower, broccoli, Romanesco cauliflower and Fioretto, the trendy elongated cauliflower-broccoli hybrid. The cool has coaxed forward their creamy, nutty flavors, and I snack while I prep, popping pieces of stem and core into my mouth. I am half full of the scraps by the time dinner is ready.

I especially love these bits. They are sweeter and juicier, I think, than the florets, silky when cooked. True, they don’t have the same textural intrigue as their crowns, and their dense, fine-grain quality isn’t quite right for every dish. But they are so good to eat that discarding them (as we are mysteriously conditioned to do) strikes me as a disservice to my palate as well as my budget.

So I save them, and a stash of brassica scraps lives almost perpetually in my fridge. (The freezer also works.) I could tuck them cozily into any number of dishes: a simple bean soup, a pot of kichidi or a pasta sauce with olives and capers. But I think they have more to offer. So with nearly every trimmings stash, I make a soup of stems and cores, a velvety, judiciously cheesy one, where their flavor and dense texture are the whole reason for the thing.

There is a little onion, for sweetness and twang, and a tiny potato — the barest needed to yield a creamy texture. Bay leaf is a gentle back note, with its sweet, harmonizing musky tone, and I include just enough cheddar cheese to bring complexity and richness without bulldozing the flavor of the vegetables. The soup cooks in water rather than broth, so the flavor of every component is bright and clear.

I make as much soup as I have trimmings, so a pot may give me one bowl, or three. If I do want to make more soup than my stems and cores will provide, I'll supplement with whatever florets I have, or scavenge the vegetable drawer for other brassicas: Kohlrabi brings its water chestnut-like sweetness, rutabaga a gently spicy, buttery effect. I suspect turnips or radishes would contribute their respective pungency, and while I have never tried them, one day they will surely make their case.

The method is brief and unfussy: I peel the stems if they’re especially tough or fibrous, then slice everything thin so the vegetables cook quickly and the flavors are gentle. (Cooking them for too long or too hard can bring out sulfurous and bitter flavors.) I sauté the onion in butter and oil, then add all the trimmings and the potato. I pour in water to barely cover and season with salt until everything tastes like soup.

If I have some stale bread, I’ll make croutons while the soup simmers, tearing a hunk into ragged pieces, coating them in melted butter and toasting them until golden and crisp. Or if there are a few leaves — kohlrabi tops or cauliflower leaves are especially good here, but any will do — I’ll wilt them in oil and water and perch them on top of the soup, in shallow bowls so they don’t sink out of sight.

Once the vegetables are barely soft — not mush, just tender to a fork — I turn the heat off and let things rest before blending into a creamy puree that may be the color of butter, cream or pistachios, depending on the vegetables that went in. Even a low-watt blender will achieve a velvety texture.

The soup is already lovely, but the cheese gives it heft. I almost always tip in cheddar, although an Alpine style such as Gruyère or Comté is a nice change. Then I stir until it melts in the residual heat. Sometimes I grate in a little nutmeg and white pepper, or just crack coarse black pepper over the top.

Each version is a little different. But each one tastes like a delicious victory.

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Scrappy Broccoli and Cauliflower Soup

1 pound stems and cores from broccoli, cauliflower or other cruciferous brassicas

1 small yellow potato (about 3 ounces)

1½ tablespoons unsalted butter

1 teaspoon neutral oil, such as peanut or canola

1 small yellow onion (4 ounces), finely diced

¾ teaspoon fine salt, plus more as needed

1 bay leaf

2½ cups water

3 ounces sharp cheddar cheese, grated (about 1 cup)

Freshly ground white or black pepper

Croutons, for serving (optional)

Peel any of the brassica stems, if they seem tough, then slice the stems and cores about ⅛-inch thick. Peel and thinly slice the potato, and place it in a bowl of water so it doesn’t discolor.

In a small (2-quart) heavy-bottomed saucepan over medium-low heat, melt the butter and warm the oil. Add the onion and a pinch of salt, and cook, stirring occasionally, until translucent and softened, 5 to 7 minutes, adjusting the heat as needed so the onion doesn’t brown.

Drain the potato and add it to the pan, along with the brassica slices, bay leaf and salt, stirring to coat in the fat. Add the water, increase the heat to medium-high and bring to a boil. Reduce the heat so the liquid is at a simmer, partially cover and cook until the vegetables are tender and can be broken with a spoon or easily pierced with a fork, 15 to 20 minutes. Remove from the heat and let cool slightly. Working in batches, as needed, puree the soup in a blender. Fill it no more than halfway, and be sure to remove the center ring from the lid and hold a kitchen towel over the lid as you blend to prevent splatters. (Alternatively, use an immersion blender to puree the soup in the pot until very creamy.)

Return the soup to the pot and gently reheat over low heat, if needed, until hot. Add the cheese and stir until fully melted. Taste, and season with pepper and more salt, if desired. Ladle the soup into bowls, top with croutons, if desired, and serve hot.

Makes 3 to 4 servings (about 4 cups)

Substitutions: For yellow onion, use white onion or shallots. For sharp cheddar cheese, use other types of cheddar cheese, or other melting cheese such as Comté or Gruyère. If you don’t have enough scraps, use full heads of cauliflower and/or broccoli.

Nutrition | Per serving (1 cup), based on 4: 197 calories, 13g carbohydrates, 34mg cholesterol, 14g fat, 3g fiber, 8g protein, 7g saturated fat, 592mg sodium, 4g sugar

— Emily Horton