Roasted Cauliflower Soup with Garlic and Thyme (Creamy Fall Soup Without Much Cream)

Why you’ll love it

• Deep roasted flavor: caramelized cauliflower and sweet roasted garlic give the soup a nutty, savory depth.
• Creamy without heavy cream: a potato and a quick blend make it velvety with only 1/2 cup of cream.
• Thrifty and make-ahead: inexpensive vegetables, easy to double and it freezes beautifully.

Quick facts

Ingredients

For the roasted cauliflower

• 1 large head cauliflower (about 2 1/2 lb / 1.1 kg), cut into 1 1/2-inch (4 cm) florets
• 8 cloves garlic, unpeeled
• 3 tbsp extra-virgin olive oil
• 1 tsp kosher salt
• 1/2 tsp black pepper

For the soup

• 2 tbsp (28 g) unsalted butter
• 1 medium yellow onion, diced (about 1 1/2 cups)
• 2 stalks celery, diced
• 1 medium Yukon Gold potato (about 8 oz / 225 g), peeled and diced
• 1 tbsp fresh thyme leaves (or 1 tsp dried thyme)
• 5 cups (1.2 liters) low-sodium vegetable or chicken broth
• 1/2 cup (120 ml) heavy cream or half-and-half
• 1 tbsp fresh lemon juice
• 1/8 tsp ground nutmeg
• Kosher salt and black pepper, to taste

For serving

• 1 cup reserved roasted cauliflower florets
• Extra-virgin olive oil, for drizzling
• Chopped fresh chives or parsley and a few thyme sprigs
• Finely grated Parmesan and crusty bread (optional)

Step-by-step method

1. Heat the oven. Place a rack in the center of the oven and heat it to 425°F (220°C). Line a large rimmed baking sheet with parchment paper.

2. Roast the cauliflower. Toss the florets and unpeeled garlic cloves with the olive oil, salt and pepper and spread them in a single layer on the baking sheet. Roast 25 to 30 minutes, stirring once halfway, until the cauliflower is tender and deeply golden on the edges and the garlic is soft.

3. Reserve the garnish. Set aside about 1 cup of the best-looking browned florets for topping. Squeeze the soft roasted garlic out of its skins and discard the skins.

4. Sauté the aromatics. While the cauliflower roasts, melt the butter in a large Dutch oven or soup pot over medium heat. Add the onion and celery and cook 6 to 8 minutes, stirring often, until soft and translucent but not browned. Stir in the thyme and cook 30 seconds.

5. Simmer. Add the diced potato, the remaining roasted cauliflower, the roasted garlic and the broth. Bring to a boil, then reduce the heat, partially cover and simmer 15 to 20 minutes, until the potato is completely tender.

6. Blend. Purée the soup with an immersion blender until completely smooth, about 2 minutes. Or let it cool 10 minutes and blend in batches in a regular blender, filling it no more than halfway and holding the lid with a towel, then return it to the pot.

7. Finish. Stir in the cream, lemon juice and nutmeg and warm over low heat 2 to 3 minutes without boiling. If the soup is too thick, add a splash of broth or water. Taste and season with salt and pepper.

8. Serve. Ladle into warm bowls and top with the reserved roasted florets, a drizzle of olive oil, chives or parsley and a little Parmesan if you like. Serve hot with crusty bread.

How to know it is done

The roasted cauliflower is ready when the florets are fork-tender and have golden brown, caramelized edges; pale cauliflower makes a bland soup. The soup is ready to blend when the potato cubes break apart easily with a spoon. After blending, the soup should be completely smooth with no grainy bits, thick enough to coat the back of a spoon but still pourable, and steaming hot all the way through (at least 165°F / 74°C if reheating).

Tips for the best result

• Do not crowd the baking sheet; use two sheets if needed so the cauliflower roasts instead of steams.
• Cut the florets about the same size so they brown evenly.
• Roast the garlic in its skin so it turns sweet and creamy instead of burning.
• Use a Yukon Gold potato; its buttery, waxy texture blends smoother than russet.
• Add the lemon juice at the end; it brightens the flavor without tasting lemony.

Variations and substitutions

• Dairy-free and vegan: use olive oil instead of butter, vegetable broth and full-fat coconut milk or cashew cream instead of the cream.
• Smoky: add 1 tsp smoked paprika to the cauliflower before roasting and top with crispy bacon or smoked paprika oil.
• Curried: stir 2 tsp curry powder and 1 tsp grated fresh ginger into the onions.
• Brown butter and sage: top each bowl with a spoonful of brown butter and fried sage leaves.
• Without potato: use 1 can (15 oz / 425 g) drained white beans for body and extra protein.
• Extra crunch: top with toasted pumpkin seeds, croutons or crispy fried shallots.

Make ahead

Roast the cauliflower and garlic up to 2 days ahead and refrigerate them in an airtight container. The finished soup tastes even better the next day: cool it, refrigerate it covered and reheat gently. For a holiday first course, make the soup completely up to 3 days ahead, leaving out the cream, then reheat it and stir in the cream just before serving. Freeze the soup without the cream for up to 3 months.

Storage and reheating

Refrigerate leftovers in an airtight container for up to 4 days. Reheat in a saucepan over medium-low heat, stirring often, until hot, adding a splash of broth or water if it has thickened. Avoid boiling after the cream is added. To freeze, cool completely and store in freezer containers, leaving 1 inch (2.5 cm) of space at the top; thaw overnight in the refrigerator and whisk or re-blend if it looks separated.