In a double broiler, melt stick of butter and add cubed cream cheese. Stir over low heat until cheese is melted. In seperate skillet, melt 2 tablespoons margarine and saute' crawfish tails, onions, bell pepper and mushrooms until seasonings are limp. Add the mushroom soup and cooked rice. Stir in garlic powder and peppers. Add the cream cheese and margarine mixture to crawfish mixture. Stir and check for seasoning. Put in greased casserole. Top with grated Velvetta cheese and fried onion rings. Bake in 350* oven for 30 minutes or until bubbly. Serves 8 to 10 . Freezes well and can be made a day before you need to serve it. Shrimp also can be substituted for the crawfish. (wrv)