1. In salted boiling water, cook rigatoni until super al dante (will finish cooking in oven). Drain and rinse in cold water.
2. In a large bowl, mix butter into pasta until well coated. Add the three cheeses and the cream. Toss well and add 1/4 cup of the parmigiano while tossing.
3. Place in a buttered casserole and sprinkle the remaining parmigiano on top. Sprinkle nutmeg over everything and bake at 375F for 15-20 mins. When the top of the pasta has turned golden brown, it is done.