Serves 6 to 8. Published March 1, 2011. From Cook's Illustrated.
To make a vegetarian version of this soup, substitute vegetable broth for the chicken broth.
|2||tablespoons unsalted butter|
|2||pounds broccoli , florets roughly chopped into 1-inch pieces, stems trimmed, peeled, and cut into 1/4-inch-thick slices|
|1||medium onion , roughly chopped (about 1 cup)|
|2||medium garlic cloves , minced or pressed through garlic press (about 2 teaspoons)|
|1 1/2||teaspoons dry mustard powder|
|pinch cayenne pepper|
|1/4||teaspoon baking soda|
|2||cups low-sodium chicken broth (see note)|
|2||ounces baby spinach (2 loosely packed cups)|
|3||ounces sharp cheddar cheese , shredded (3/4 cup)|
|1 1/2||ounces Parmesan cheese , grated fine (about 3/4 cup), plus extra for serving|
|Ground black pepper|
1. Heat butter in large Dutch oven over medium-high heat. When foaming subsides, add broccoli, onion, garlic, dry mustard, cayenne, and 1 teaspoon salt. Cook, stirring frequently, until fragrant, about 6 minutes. Add 1 cup water and baking soda. Bring to simmer, cover, and cook until broccoli is very soft, about 20 minutes, stirring once during cooking.
2. Add broth and 2 cups water and increase heat to medium-high. When mixture begins to simmer, stir in spinach and cook until wilted, about 1 minute. Transfer half of soup to blender, add cheddar and Parmesan, and process until smooth, about 1 minute. Transfer soup to medium bowl and repeat with remaining soup. Return soup to Dutch oven, place over medium heat and bring to simmer. Adjust consistency of soup with up to 1 cup water. Season to taste with salt and pepper. Serve, passing extra Parmesan separately.