In a heavy skillet, brown the ground beef in 2 Tbsps. of butter, then add the onion, red and green bell pepper; saute until soft. Spoon off excess fat, then stir in the garlic, salt, black pepper, sherry and the parsley, saute another 5 minutes
Spread the mixture into a buttered, 2 1/2 quart casserole dish.
To the cooked potatoes add the remaining 2 Tbsps. of butter and milk, beat until smooth, salt to taste.
Spread the potatoes over the meat mixture evenly, then using a spoon, pull up points. Sprinkle the top with the shredded cheese. Bake uncovered at 350 until potatoes and cheese is lightly browned.