This is a simple but beautiful way to cook sweet potato.
Use a large non stick frying pan with a lid. Wash one or two large sweet potatoes, and leave them unpeeled. Slice each sweet potato into thick pieces. Use only a little olive oil or vegetable oil, about one or two tablespoons. Heat the oil on a medium high heat, then place the pieces of potato into the pan. After about a minute, turn each piece over. Place the lid on and cook the potato pieces, on a medium low heat, until they are soft, about 30 to 40 minutes. Turn the pieces over every 20 minutes. Turn out onto a platter.