Brown ground beef in large nonstick skillet on medium-high heat. Drain fat.
Mix Gravy Mix and water in small bowl. Pour over beef. Bring to boil. Add peas and carrots. Reduce heat to low; simmer 5 minutes. Transfer meat mixture to 1 1/2-quart baking dish. Top with mashed potatoes.
Bake in preheated 350°F oven 30 minutes or until gravy bubbles and potatoes are slightly browned. Sprinkle with parsley, if desired.