Step 1Cook the peas according to the package directions, drain and set aside.
Step 2Melt the butter in a soup pot over medium-low heat. Add the green onions and salt and cook, stirring, until just softened, 3 minutes. Add the lettuce and 1/2 cup water, cover and cook over very low heat until very soft, 5 to 7 minutes. Add the stock and 1 cup of water and bring to a boil. Reduce the heat and simmer 5 minutes.
Step 3Working in batches, transfer the lettuce mixture, peas and mint to the blender and process until smooth. Transfer to a clean pot and add the cream. Simmer 5 minutes. Season with more salt if needed and white pepper to taste. Ladle into bowls and garnish with pea shoots.