From "5 Spices, 50 Dishes" by Ruta Kahate. You can use raw beef for this, but the far more useful trick is to use leftover beef or lamb roast. (Author suggested beef roast, but I tried it with lamb and it was great). I think you could also use rare deli beef also, for a quick meal. And I'll make potatoes like this even if not making the rest of the dish. This is a popular dish reflecting the influence of the many cultures that colonized India.