How long do you boil a potato?

When I make sweet potato pie I bake the potatoes for 45 to 55 minutes. Or until soft on the inside. Soft enough to pierce with a fork. Or you can boil them for 15 to 20 minutes. Just do as you do with regular potatoes. Boil until you can pierce with a fork and it's soft enough to fall apart. But not too soft to be really mushy.