The secret to the best cauliflower soup? High heat and a little spice.
By Melissa Clark
It’s hard for me to look a head of cauliflower in the florets and not immediately want to cut it up and throw it in the oven.
When doused in oil and exposed to high heat, all the little crevices and fractals covering the surface — sometimes called curd because of its resemblance to cheese — sizzle until brown and wonderfully crisp. I can easily eat a half sheet-pan of roasted cauliflower on its way from oven to table, snacking on the burnished nuggets, one after the other, like potato chips.
And this is the reason cauliflower soup is a rarity in my kitchen. Why simmer the vegetable in broth when roasting it is just so grand?
This creamy cauliflower soup, however, is an exception — precisely because I roast the florets before submerging them in the broth.
The initial cooking browns the pieces, intensifying their inherent sweetness. Then, I simmer them in broth until they collapse and turn thoroughly soft. When puréed, they give the soup a rich, velvety texture that’s creamy without any dairy products.
On its own, the soup is gentle and restrained. So I usually punch it up with a bold, tangy garnish. For this version, I glazed some plum tomatoes with harissa and roasted them along with the cauliflower.
Under high heat, the tomatoes condensed, turning jammy beneath their fiery coating. Those contrasting flavors — the sweet and spicy tomatoes next to the mild, cozy soup — are what makes this so fun to eat. Every bite is a little different, some mellower, some zippier.
One thing to keep in mind: Harissa pastes vary a lot in their heat level, so taste yours before brushing it on the tomatoes. If it seems at the moderate end of the continuum (meaning you don’t immediately reach for a piece of bread to soothe your tongue), use the full amount listed. But if you’re working with a more intensely fiery paste, use the lesser amount. You can always add more later. (If you’re using a harissa powder, you can mix it with some oil to create a paste.) And if you don’t have harissa on hand, any other chile paste will work well.
It’s best to keep the tomatoes and soup separate until serving. That way, the tomatoes stay brightly scarlet in a sea of beige; it’s a soup that looks as vivid as it tastes.
Creamy cauliflower soup with harissa tomatoes
Cauliflower is cooked twice for this plush vegan soup, which is both cozy and complex in flavor. First, it’s roasted so its flavor deepens, simmered in broth until thoroughly and completely soft. When puréed, it gives the soup a rich, velvety texture and a savory, caramelized character that’s zipped up with harissa-glazed roasted tomatoes. A note on harissa pastes: They vary a lot in their heat level. If yours is milder, use the full amount listed, but if you’re working with a more fiery harissa, use less. And if you don’t have harissa on hand, any other chile paste will work well.
Yield: 6 servings
Total time: 1 hour 15 minutes
1 large head cauliflower (about 3 pounds), trimmed and cut into 1-inch florets (about 12 cups)
Kosher salt (such as Diamond Crystal) and freshly ground black pepper
1 1/4 teaspoons ground coriander
7 tablespoons extra-virgin olive oil, plus more for serving
1 small bunch thyme (about 10 sprigs)
1 pound plum tomatoes, halved, seeds scooped out
2 to 4 tablespoons harissa paste
3 large bunches scallions, whites and greens thinly sliced (about 2 1/2 cups)
1 jalapeño, seeded (if desired) and coarsely chopped
4 large garlic cloves, finely chopped
1 1/2 teaspoons ground cumin
1 tablespoon tomato paste
6 cups vegetable stock
3/4 cup chopped cilantro leaves and tender stems, plus more for optional garnish
1. Heat oven to 425 degrees and line 2 sheet pans with parchment paper.
2. In a large bowl, combine cauliflower, 1 teaspoon salt, a large pinch of black pepper, 3/4 teaspoon ground coriander, 3 tablespoons oil and half the thyme sprigs, tossing everything until well coated. Spread the cauliflower evenly across one of the prepared pans.
3. Using the same bowl (no need to wash it first), combine halved tomatoes, 1 to 2 tablespoons of harissa (depending on how spicy your harissa is; taste it first), 2 tablespoons olive oil, a large pinch of salt and the remaining thyme sprigs, and toss gently until the tomatoes are well coated. Spread tomatoes on the other baking sheet, cut-side up.
4. Place both sheet pans in the oven and roast for 20 minutes, then stir the cauliflower but not the tomatoes. Continue to roast until cauliflower is golden brown and tender, 15 to 20 minutes longer (35 to 40 minutes total roasting time). Transfer cauliflower pan to a rack, and discard thyme sprigs.
5. Using tongs, gently flip tomatoes over so their cut sides are down. Using the tongs, pinch off the tomato skins — they should slip right off — and discard. Brush 1 to 2 more tablespoons of harissa onto tomatoes and continue to roast until shriveled and condensed, about 15 to 25 minutes (35 to 45 minutes total roasting time).
6. While tomatoes are roasting, make the soup: In a large pot, heat the remaining 2 tablespoons oil over medium. Add scallions (saving 1/4 cup scallions for serving) and jalapeño, and cook, stirring occasionally, until soft and lightly colored, 5 to 7 minutes. Stir in garlic and cook for 1 minute. Add another 1 1/2 teaspoons salt, black pepper to taste, cumin and tomato paste, and cook until tomato paste darkens and caramelizes, 2 to 3 minutes.
7. Stir in roasted cauliflower and stock, and bring to a simmer. Cook, partly covered, over medium-low heat until all vegetables are very tender, 15 to 20 minutes. Turn off the heat. Using an immersion blender, purée the soup until smooth. (Alternatively, you can purée it in batches in a food processor or blender.)
8. Transfer the roasted tomatoes into a mixing bowl and add cilantro. Using a Microplane or other fine grater, grate zest from about half the lemon into the bowl, then stir in 1/2 teaspoon coriander and reserved scallions.
9. Using a fork or spoon, break up some of the tomatoes as you combine everything. Cut the lemon in half and squeeze a little into the tomatoes, then taste and add more salt and lemon juice as needed. It should taste well seasoned and a little tangy.
10. To serve, squeeze in the juice from half the lemon. Taste and add salt, pepper and lemon if needed. Ladle soup into individual bowls and dollop harissa tomatoes on top; top with olive oil and more cilantro, if you like.