Two cups of basmati rice; wash rice 6 times or until water is clear. This will assure that all surface starch is washed away. Boil 12 cups of water with 1/2 cube of butter and 1 teaspoon of salt. Add rice and boil rice until firm but not cooked; test rice by biting on it. When you can bite through it but it remains firm it is ready.

Remove rice from burner and drain in colander. Wash until water is clear to remove surface starch. Melt remaining 1/2 cube of butter in large pot with a pinch of saffron. Re-add rice to melted butter and fold in to coat all the kernels of rice.

Put paper towel over top of pot and place lid over paper towel - turn heat to lowest setting. Change towel every 10-15 and steam for 45-60 minutes. Serve with butter and sumac to taste.