Potato-Topped Sloppy Joe Casserole

1 lb lean ground beef
1/2 cup chopped onion
1/2 cup chopped green pepper
1 (15-oz) can sloppy Joe sandwich sauce
1-1/2 cups frozen corn
2 cups water
1/4 tsp garlic salt
2 cups mashed potato flakes
1/4 cup sour cream
1 egg, beaten
1/2 cup shredded Cheddar cheese

Heat oven to 325º In large skillet, brown ground beef, onion and bell peppers over medium-high heat until beef is thoroughly cooked. Drain. Add sandwich sauce and corn; mix well. Reduce heat; simmer 4 to 6 minutes or until thoroughly heated and corn is crisp-tender, stirring occasionally. Meanwhile, in another saucepan, bring water and garlic salt to a boil. Remove saucepan from heat; stir in potato flakes until well-blended. Add sour cream and egg; mix well. Spoon beef mixture into ungreased shallow 2-quart casserole. Spoon potato mixture in circle around edges of casserole. Sprinkle potatoes with the shredded Cheddar cheese. Bake at 325º for 25 to 30 minutes or until potatoes are set. (If desired, sprinkle potatoes with chopped fresh parsley). Serves 4