Spooky Shepherds Pie

Name: Spooky Shepherd's Pie
Ingredients: 1 pound lean ground beef; 1 medium onion; 2 1/2 cups frozen mixed vegetables; 14 1/2 ounces diced tomatoes with italian herbs; 12 ounces beef gravy; 1 3/4 cups water; 2 tablespoon butter or margarine; 1/4 teaspoon garlic powder; 1/2 cup milk; 2 1/4 cups plain mashed potato mix (dry); 1/4 cup grated parmesan cheese; 1 egg