In a skillet melt butter over medium-high heat. Sautee the onion, parsley, and basil until onion is tender. Add zucchini and continue to cook for 2 minutes. Remove from heat, stir in crumbs, egg, cheese, salt and pepper.
Carefully loose the skin of each chicken breast as one side to form a pocket. Stuff each with the zucchini mixture. Bake at 325 degrees for 50-60 minutes or until chicken juices are clear.
Stuffing can also be baked separately and served as a side dish.