Ingredients
3 tablespoons butter
1 1/2 cups coarsely chopped shallots (about 6 large)
1/2 teaspoon dried thyme
3 tablespoons all-purpose flour
Coarse salt
3 pounds asparagus, trimmed and cut into 1-inch pieces
1/3 cup heavy cream
2 to 3 tablespoons fresh lemon juice
Preparation
In a large (4-quart) saucepan, melt butter over medium heat. Add shallots and thyme; cook until shallots are soft, about 5 minutes. Add flour; cook until incorporated, stirring constantly, about 1 minute.
Add asparagus and 6 cups water; season generously with salt. Cover, and bring to a boil.
Reduce heat; cover, and simmer, until asparagus is bright green and just tender, 2 to 4 minutes. Working in small batches, purée soup in a blender until very smooth. To prevent splattering, fill blender only halfway, and allow heat to escape: Remove cap from hole in lid, and cover lid with a dish towel. (To freeze, see note.) If serving right away, stir in cream and lemon juice.