For an extra touch of flavor, consider adding sun-dried tomatoes or roasted red peppers to the stuffing. If you don't have mozzarella string cheese, shredded mozzarella can be used instead. Serve with a side of roasted vegetables or a light salad for a complete and balanced meal. Feel free to experiment with different types of pesto, such as sun-dried tomato pesto or basil pesto. Chicken breasts can be pounded to an even thickness before stuffing to ensure even cooking.