Heat oven to 350 degrees. In skillet, cook ground beef and onion until meat is no longer pink, drain. Stir in 1/2 teaspoon salt, pepper, green beans and soup. Spoon into 1 1/2 quart casserole. Set aside. In saucepan, heat water, margarine and 1/4 teaspoon salt to rolling boil. Remove from heat. Stir in milk and potato flakes with fork until potatoes are desired consistency. Stir in eggs. Spoon potatoes in mounds over meat mixture. Sprinkle with cheese. Bake at 350 degrees for 25-30 minutes.
