Creamy Cauliflower Soup

From America's Test Kitchen Season 14: Let’s Start with Soup

WHY THIS RECIPE WORKS:

For a creamy cauliflower soup without cream, we relied on cauliflower’s low insoluble fiber content to produce a velvety smooth puree. To ensure that cauliflower flavor remained at the forefront, we cooked the cauliflower in seasoned water (instead of broth), skipped the spice rack entirely, and bolstered the soup with sautéed onion and leek. We added the cauliflower to the simmering water in two stages so that we got the grassy flavor of just-cooked cauliflower and the sweeter, nuttier flavor of long-cooked cauliflower. Finally, we fried florets in butter until both browned and used each as a separate, richly flavored garnish. 

The secret to the best-tasting cauliflower soup you’ve ever eaten? Undercook some of the cauliflower—and overcook the rest.

Serves 4 to 6

White wine vinegar may be substituted for the sherry vinegar. Be sure to thoroughly trim the cauliflower’s core of green leaves and leaf stems, which can be fibrous and contribute to a grainy texture in the soup.

INGREDIENTS

• 1 head cauliflower (2 pounds)
• 8 tablespoons unsalted butter, cut into 8 pieces
• 1 leek, white and light green parts only, halved lengthwise, sliced thin, and washed thoroughly
• 1 small onion, halved and sliced thin
• Salt and pepper
• 4 1/2 – 5 cups water
• 1/2 teaspoon sherry vinegar
• 3 tablespoons minced fresh chives

Directions

1. Pull off outer leaves of cauliflower and trim stem. Using paring knife, cut around core to remove; thinly slice core and reserve. Cut heaping 1 cup of 1/2-inch florets from head of cauliflower; set aside. Cut remaining cauliflower crosswise into 1/2-inch thick slices.
2. Melt 3 tablespoons butter in large saucepan over medium-low heat. Add leek, onion, and 1 1/2 teaspoons salt; cook, stirring frequently, until leek and onion are softened but not browned, about 7 minutes.
3. Increase heat to medium-high; add 4 1/2 cups water, sliced core, and half of sliced cauliflower; and bring to simmer. Reduce heat to medium-low and simmer gently for 15 minutes. Add remaining sliced cauliflower, return to simmer, and continue to cook until cauliflower is tender and crumbles easily, 15 to 20 minutes longer.
4. While soup simmers, melt remaining 5 tablespoons butter in 8-inch skillet over medium heat. Add reserved florets and cook, stirring frequently, until florets are golden brown and butter is browned and imparts nutty aroma, 6 to 8 minutes. Remove skillet from heat and use slotted spoon to transfer florets to small bowl. Toss florets with vinegar and season with salt to taste. Pour browned butter in skillet into small bowl and reserve for garnishing.
5. Process soup in blender until smooth, about 45 seconds. Rinse out pan. Return pureed soup to pan and return to simmer over medium heat, adjusting consistency with remaining water as needed (soup should have thick, velvety texture but should be thin enough to settle with flat surface after being stirred) and seasoning with salt to taste. Serve, garnishing individual bowls with browned florets, drizzle of browned butter, and chives and seasoning with pepper to taste.

TECHNIQUE

CREAMY BY NATURE

Most soups made from pureed vegetables contain cream for a simple reason: to mitigate the effects of insoluble fiber. All vegetables have both soluble and insoluble fiber, but only the soluble kind fully breaks down during cooking, which contributes viscosity to the soup. Insoluble fiber remains intact, and the best that the blades of a blender can do is break it down into smaller bits. But cauliflower has a leg up on other vegetables. It’s very low in overall fiber—and only half of it is insoluble. This means that cauliflower is easily pureed into a silky-smooth soup with no cream at all.