• 1 lb green asparagus
• 1 large onion, chopped
• 3 tablespoons unsalted butter
• 2.5 cups chicken broth
• 1/4 cup heavy cream
• 1/2 teaspoon salt
• 1/4 teaspoon pepper
• Cut asparagus into 1/2-inch pieces.
• Cook onion in s butter in a heavy pot over moderately low heat, stirring, until softened.
• Add asparagus pieces and salt and pepper to taste, then cook, stirring, 5 minutes.
• Add chicken broth and simmer, covered, until asparagus is very tender, 15 to 20 minutes.
• Purée soup in batches in a blender until smooth, transferring to a bowl, and return to pan.
• Stir in heavy cream.
• Season with salt and pepper.
Soup keeps, covered and chilled, 2 days.