1Heat oven to 375°F. In 12-inch skillet, cook beef and onion over medium heat 8 to 10 minutes, stirring occasionally, until thoroughly cooked; drain. Set 12 peas (from frozen vegetables) aside for garnish. Add remaining frozen vegetables, tomatoes and gravy to beef mixture. Heat to boiling. Reduce heat to medium-low. Cover and cook 8 to 10 minutes, stirring occasionally, until vegetables are crisp-tender.
2Meanwhile, in 2-quart saucepan, heat water, butter and garlic powder to boiling. Remove from heat; add milk. Stir in dry potatoes; blend well.
3Spoon beef mixture into ungreased 8-inch square (2-quart) or oval (2 1/2-quart) glass baking dish. With large spoon, make 6 mounds of potato mixture on top of beef mixture to look like ghosts. Place 2 reserved peas on each mound to look like eyes. Bake 20 to 25 minutes or until potatoes are set and mixture is hot.