Melt 1 stick butter in casserole dish. Add 1 large diced onion; 2 stalks celery, diced (optional); 2 medium cans button mushrooms. Saute for 3 minutes. Add 1 1/2 cups uncooked regular rice. Saute 1 minute. Pour 2 cans undiluted beef consomme soup. Cover casserole dish and cook for 1 hour at 350 degrees.