Mixed potato augratin

1 yam, about 1 1/2 lbs., peeled and thinly sliced
1 sweet potato, about 1 1/2 lbs., peeled and thinly sliced
2 russets, about 2 lbs., peeled and thinly sliced
1 red onion, thinly sliced
4 TBSP. butter, cut into small pieces
1 TBSP. dried thyme
1/2 tsp. ground nutmeg
1 TBSP. salt
1/2 tsp. black pepper
2 cups heavy cream
2 cups grated Gruyere, Swiss or Emmanthaler cheese (I just used mozzarella because that is what I keep on hand)

Place the sliced potatoes in a mixing bowl: toss well. Grease a 2 quart baking dish. Place 1/2
of the potatoes in the dish and top with 1/2 of the sliced onions and dot with 1/2 butter. Layer remaining potatoes, onions and butter in top. In a mixing bowl combine thyme, nutmeg, salt, pepper, cream and cheese. Pour over the potatoes and cover with foil. Bake at 375 for 1 hour, remove foil and bake an additional 5 minutes. Serves 10-12

orginally found as Dave Litti"Coat Your Potatoes with this Au Gratin"