In the restaurant world we cook rice in great quantities and it must be perfect and look pretty. If you don’t know how to cook rice in quantity you better ask the chef because if you mess up it might cost you your job or at the least you will be the object of ridicule.
Use good long grained rice. Better brands like Uncle Ben’s has been washed at the factory, cheaper types, including bulk oriental brands need to be washed and rinsed well to eliminate starch on the kernel and dirt and debris from the product.
In a large saucepan sauté a small dice of onion, carrot and celery (or pulse these in a food processor), this is called a mirepoix, use one cup for each four cups of raw rice. Sauté 2 cups of the veggies in oil or butter until they begin to soften add eight cups of raw rice and continue to cook until all the rice is coated with oil and the vegetables are well incorporated. If you want to color the rice now is the time to add strands of saffron (if you are wealthy) or a tablespoon of turmeric (if you are frugal) stir until the rice yellows. Put the rice mixture into a 4 inch deep half hotel pan (or other similar casserole dish) add 12 cups salted water or stock. Cover the hotel pan with foil and put it into a 350 degree oven for 45 minutes. Even better than an oven is a professional pressurized steamer, steam heat eliminates any possibility that any kernels will dry out. When you take the rice out of the oven immediately take off the foil covering, when the trapped steam disperses fluff the rice with a large serving spoon. The rice is ready for service or will hold for hours on a steam table or double boiler.