Cook meat and onions in 1/4 cup bouillon until well done. Drain and season. Place mixture in an 8 by 11 inch baking pan, cover with layer of carrots and peas. Prepare two cups medium thick gravy using bouillon to flavor. Pour hot gravy over meat and vegetables. Mash potatoes, seasoning with a little milk, salt, and pepper. Spread potatoes over meat mixture and dot the top with butter. Bake 1 hour in a preheated 300 degree oven.