Preheat the oven to 350 degrees F. Peel and chop potatoes. Place in water and boil until soft (15 - 20 minutes).
Chop the onions and garlic. Use 2 tsp. of butter and brown the garlic and onion until clear. Add ground beef and brown.
In a bowl mix the soup with 1/2 can of heavy cream. Mix in the mushrooms. Combine the meat and the soup mixture. Pour into the bottom of a baking dish. When potatoes are soft, mash with 2 tsp. of butter and milk. Place the mashed potatoes over the meat/soup mixture. Cover the potatoes with cheese.
Put in the oven for 30 minutes or until cheese is melted to desire consistency.