Active time: 20 min Start to finish: 25 min

Ingredients

　　1 small onion, finely chopped

　　2 garlic cloves, finely chopped

　　2 tablespoons unsalted butter

　　1/3 cup dry white wine

　　2 lb mussels (preferably cultivated), scrubbed and beards removed

　　1/2 cup heavy cream

　　3/4 cup loosely packed fresh basil leaves

　　1/4 teaspoon black pepper

　　Cook onion and garlic in butter in a 5- to 6-quart heavy pot over moderately low heat, stirring, until softened, 3 to 5 minutes. Add wine and mussels and cook, covered, over moderately high heat until mussels just open wide, 6 to 8 minutes. (Discard any mussels that have not opened after 8 minutes.) Transfer mussels with a slotted spoon to a serving bowl, then transfer cooking liquid to a blender along with cream, basil, and pepper and blend until smooth (use caution when blending hot liquids). Season sauce with salt and pour over mussels.