Melt the butter in a medium skillet over medium heat. Add about 1 tablespoon olive oil and the sliced scallions. Cook for a few minutes, or until the scallions are softened. Meanwhile, slice the lettuce leaves, saving a few tender inner leaves to add at the end. Turn the heat up and add the peas, sliced lettuce, and a pinch of salt and pepper. Cook for 1 minute, then sprinkle in the flour and stir until everything is lightly coated. Slowly pour in the stock, then cover and turn the heat up to high. Cook for 4 minutes or until the peas are tender.
Taste and add another pinch of salt or pepper if needed. Pick the mint leaves, finely chop, and sprinkle into the pan. Add the lemon juice. Slice the reserved lettuce leaves, then scatter those on top and serve immediately with a tiny drizzle of extra virgin olive oil. Makes 8 servings.