Step 1In 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.
Step 1Blanch the shelled peas in a pot of boiling water just until tender, 1 to 2 minutes. Drain and chill in an ice water bath to stop the cooking process. Drain again and set aside.
Step 2Cook the bacon in a sauté pan until crisp. Stir in the leek cream, peas and onions, and bring to a boil. Reduce the heat and stir in the lettuce. Season with ¼ teaspoon salt and 1/8 teaspoon pepper, or to taste. Remove from heat and serve immediately.