Cook chicken until tender in water to cover with onion and 1 1/2 tsp. salt added. Cool chicken ( reserving broth); remove skin and cut chicken meat in small pieces with kitchen scissors.
Melt chicken fat in saucepan. Stir in flour; add 4 c. liquid (juice drained from mushrooms and chicken broth) and evaporated milk. Cook and stir until sauce is thick and smooth. Add 1 tsp. salt, pepper, turmeric, and oregano.
Combine rice with boiling water; add 1 1/2 tsp. salt and butter. Cover and bake in a hot oven (400°) 30 minutes, or until tender.
Spread rice in the bottom of a large casserole or baking dish. Top with chicken, then with green onions, sauce, and mushrooms; sprinkle cheese over top.
Bake in moderate oven (350°) 30 minutes.
Yield: Makes 10 to 12 servings.