Ingredients

• 1 large head romaine (1 1/2 pound)
• 1 medium onion, chopped
• 2 tablespoons unsalted butter
• 1/2 teaspoon finely chopped garlic
• 1 (10-ounce) package frozen peas (2 1/4 cups)
• 1 cup chicken broth
• 1 1/2 cups water
• 3/4 teaspoon salt
• 1/8 teaspoon black pepper
• 1 tablespoon chopped fresh dill
• 1/4 cup heavy cream

Instructions

1. Separate dark green outer leaves of romaine from pale green inner leaves and coarsely chop enough dark green leaves to measure 6 cups loosely packed. (Reserve heart for another use.)
2. Cook onion in butter in a 3- to 4-quart heavy saucepan over moderate heat, stirring occasionally, until softened, about 5 minutes. Add garlic and cook, stirring, 1 minute. Add lettuce and cook, stirring, until wilted, about 2 minutes. Add peas, broth, water, salt, and pepper and simmer, uncovered, 10 minutes.
3. Purée soup in 2 batches in a blender with dill and cream (use caution when blending hot liquids).