Springy Chicken Soup

Torn romaine lettuce wilts slightly in the soup and has a lighter, fresher, and less earthy taste than juicier greens like spinach or kale. Slice the carrots in the same shape and thickness as the leeks, so that both vegetables are combined in each spoon.
Preheat a large roasting pan over medium-high heat. Add 1 1/2 teaspoons butter; whisk to coat. Add the chicken; cook for 6 minutes or until lightly browned, stirring occasionally. Remove the chicken from the pan.Add the remaining 1 tablespoon of oil to the pan; stir to coat. Add the leeks and carrots; simmer for 5 minutes. Add the broth and thyme and bring to a boil. Cover and cook for 8 minutes or until the carrots are almost tender. Add the chicken, peas, pepper and salt; cook for 3 minutes. Remove thyme; discard. Remove the pan from the heat; add the lettuce leaves and parsley. Pour 1 1/2 cups of soup into each of the 4 bowls; sprinkle each serving with 1 tablespoon of cheese.