Mince the onion. Mince the mushrooms, and the chicken together. Cook the onion in 4 T of melted butter. When onions are done add the chicken-mushroom mixture and cook for 5 minutes aqdding salt & pepper to taste. Remove frm the heat and stirin the sour cream and the nutmeg. Preheat the oven to 400 degrees F. Spoon the chicken mixture into 4 ramekins and sprinkle with grated cheese. Bake for 10 minutes the serve hot.