Preheat broiler. Prepare 4 servings of mashed potatoes according to package directions, using milk, margarine and 1/2 teaspoon salt.

Meanwhile, brown beef in large broilerproof skillet over medium-high heat, stirring to break up meat. Drain fat. Sprinkle beef with remaining 1/2 teaspoon salt and pepper. Add gravy and vegetables; mix well. Cook over medium-low heat 5 minutes or until hot.

Spoon prepared potatoes around outside edge of skillet, leaving 3-inch circle in center. Sprinkle cheese evenly over potatoes. Broil 4 to 5 inches from heat 3 minutes or until cheese is golden brown and beef mixture is bubbly.