Step 1 In a heavy saucepan, sweat the leeks in the butter until softened, about 8 minutes. Stir in the cream, 1/8 teaspoon each salt and pepper and a scant 1/8 teaspoon nutmeg, or to taste. Simmer for 2 to 3 minutes to marry the flavors, then remove from heat and purée. This makes about 1 cup cream.