I have always loved to eat sweet potatoes and yams, but they always came out of the oven tough and dried out. My wife and I had ordered a sweet potato as part of our meal at an Outback Steakhouse. When it arrived it was not only sweet but moist and delicious. It just melted in our mouths.
When the waiter came to asked how everything was, we inquired what was their secret to cooking such delicious sweet potatoes. To our amazement, he told us that they rub cooking oil on the sweet potato then wrap them in foil before they place them in the oven. The oil keeps the skin from drying out and the foil locks in the moisture.
Make sure when you wrap the sweet potatoes in foil, that you have a cookie sheet underneath them in the oven. They are so moist, it is not uncommon for the moisture to leak out of the foil and on to the bottom of your oven. All you have to remember is the oil and foil. I guess that is why Popeye said, “I yam what I yam!”