Bring 3 cups water to a boil, add rice and cook 45 minutes. Meanwhile, saute oignons (onions) and celery in a small amount of water until tender. Add tomatoes and mushrooms and bring to a boil, then simmer. Mix flour, seasonings and remaining water in separate bowl and then add to vegetables. Cook 3 minutes, or until thick. Add peas. Pour into an 8 cup casserole dish. Cover with rice and cook for 20 minutes, at 350%f.