One of the wonderful things about cooking is how even a small change in technique can produce remarkably different results. In this smooth and creamy soup, that technique is the simple step of roasting the cauliflower before simmering and blending it, which adds a sweet and nutty dimension to the vegetable’s otherwise mild flavor, making it feel just a touch more autumnal in that warm and comforting way.
This isn’t my first foray into the world of puréed cauliflower, both roasted and not—I once published two recipes for cauliflower purée where roasting was the differentiating factor. At the time, I described my unroasted purée as silky and restrained, while the roasted version was more complex and nutty. But perhaps more relevant to this recipe is that I made clear that the difference between a cauliflower purée and a cauliflower soup is nothing more than thickness—the method for making each is the same, the only real difference is how much liquid you add to thin the puréed vegetables.
That’s the beauty of understanding technique: Two things that might seem different reveal themselves to be almost exactly the same. This means that just about everything I said for those purée recipes applies here: You want to sweat your aromatics, then add the cauliflower and simmer it in a flavorful liquid like stock, and finally blend it all to a smooth and silky finish.
I only really have a couple important notes to add for this soup:
- Roast the cauliflower at very high heat, which ensures optimum browning. In this recipe, I make a point of cutting the cauliflower into relatively large florets. This helps preserve some of the more moist interior of the vegetable and avoids it drying out excessively in the oven during roasting while still exposing enough surface area for the oven’s heat to brown the exterior well.
- The liquids are flexible, but try to use something flavorful and not just water. I think chicken stock works really well here, but anyone who wants to keep this vegetarian can use a rich vegetable stock instead. I also add cream for some extra richness, but if you’d like to make this vegan you can simply omit it and use more stock or broth.
- Pay attention to the soup’s consistency and adjust accordingly. I deliberately start with too little liquid and then thin the soup more fully only after blending. I find that this approach ensures that every batch of soup ends up with the consistency you want while accounting for personal preference and variables like evaporation during cooking. If the soup is too thick (it will be), thin it with more liquid. You really shouldn’t run into a too-thin issue with this recipe unless you accidentally over-dilute it, so…don’t do that.
- I’d almost go as far as to say the garnish on a puréed soup like this one is as important as the soup itself, giving it a clearer identity and layering additional textures and flavors that the soup itself can’t deliver. To give the relatively simple roasted cauliflower soup base here more interest, I garnish it with a whipped, curry-spiked sour cream. The spices work very well with the roasted cauliflower, while the sour cream’s tang adds an important bright note. That said, you should feel free to experiment with other garnishes; they’re an easy way to keep a soup like this feeling new and exciting even if you’ve been eating it for many days straight.
All in all, this is a soup that’s easy enough to whip up on a weeknight, but also would feel very at home as a starter for a fall or winter holiday meal.
For the Soup: Preheat oven to 500°F (260°C) and set racks in upper and lower third positions. Divide cauliflower evenly between 2 rimmed baking sheets. Drizzle 6 tablespoons (90ml) olive oil all over both sheets of cauliflower, season all over with salt, then toss to coat evenly. Spread cauliflower in a single even layer on each sheet. Roast cauliflower, stopping once halfway through to rotate trays top to bottom and flip cauliflower florets, until cauliflower is well browned, about 25 minutes. (If you only have one rimmed baking sheet, you can roast the cauliflower in two successive batches.)
Meanwhile, in a 4- or 5-quart saucepan, heat remaining 3 tablespoons (45ml) olive oil over medium-high heat until shimmering. Add onion, celery, and garlic, season lightly with salt, and cook, stirring, until softened but not browned, about 6 minutes; reduce heat if needed to prevent scorching.
Add roasted cauliflower to pot along with sage and stock or broth. Bring to a simmer over high heat, then reduce heat to maintain simmer and cook until all vegetables are very soft, about 20 minutes. Discard sage.
Carefully transfer vegetables and liquid to a blender jar, cover with blender lid with the center cap removed, and cover with a clean kitchen towel. Starting at the lowest speed and gradually increasing speed as needed, blend soup until very smooth, at least 1 minute; blend in batches if your blender jar can’t hold all the soup vegetables and liquid at once. The soup will be thick at this point and may require some stirring in the blender jar to ensure it is fully blended. (If desired, you can also use an immersion blender and blend the soup directly in the pot.)
Return blended soup to the rinsed and wiped-out pot and stir in cream. Thin with additional stock/broth or water as needed to reach desired soup consistency (it should be thick and silky, but still flow like a liquid). Season with salt and pepper to taste. Bring soup to a simmer when ready to serve.
Meanwhile, for the Curry Cream: In a large mixing bowl or the bowl of a stand mixer fitted with the whisk attachment, whisk cream, sour cream, curry powder, and a large pinch of salt until soft peaks form.
Ladle hot soup into bowls, garnish each with a generous dollop of curry cream and serve.
Notes
The better and more flavorful the broth you use, the better the soup will be. Homemade stock is always best, but store-bought will work in the interest of speed. Since it may be inconvenient to use a second quart of stock just to thin the soup, you can thin it with water instead, though this will dilute flavor more than stock will.
Use any curry powder you wish, and feel free to adjust to taste based on the curry powder you use, as their flavor and intensity can vary from type to type and brand to brand. You do want the curry cream to be strongly flavored, as it melts into the soup and will be diluted by it.
Make-Ahead and Storage
The soup can be fully made through step 5, then cooled and refrigerated in an airtight container for up to 5 days. Reheat before serving, thinning with additional stock or water if necessary.
The curry cream will weep liquid if made too far in advance, but can be prepared and refrigerated up to 3 hours in advance.