Potato-filled Samosas

The dumpling of India, and one of the best, because the dough, which is made with butter and yogurt, is rich and tangy. Traditionally, it is made by cutting the cold butter into bits and rubbing it and the flour very quickly between your fingers: Pick it up, rub it, and drop it. (If the mixture begins to feel greasy, refrigerate it for a few minutes before proceeding.) The food processor may not be as charming, but it's much easier. Take your pick.

Samosas are usually deep-fried, but you can ba