Preheat oven to 350°F. 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.
Prepare mashed potatoes according to package directions, stirring in garlic powder, onion powder and black pepper. Spread mashed potatoes evenly over meat mixture in dish.
Bake 30 minutes or until gravy bubbles and potatoes are slightly browned. Sprinkle with parsley, if desired.