We just love these! My Mom introduced them to us as part of the South Beach Diet, but they are a wonderful appetizer or side dish for non-dieters as well. The feta and sweet potatoes complement each other beautifully, and the feta isn't too overpowering as it sometimes can be.
3 long, thin sweet potatoes
1 pkg. feta cheese (I believe I use a 4 oz. pkg, but it might be 6 oz)
Preheat oven to 425 degrees. Cut sweet potatoes into discs about 1/2 inch thick. Scoop out a small dish-shape in the middle of each disc, being careful not to cut through the bottom of the potato. Toss with a small amount of olive oil and salt to taste. Spread in a single layer on a cookie sheet and roast for 15-25 minutes until tender. (But not too tender! You'll still be cooking them a bit more, so take that into account.) Combine feta cheese with a couple of teaspoons of olive oil to make a thick paste. Scoop a small amount into the center of each sweet potato round and bake at 350 degrees for another 5 minutes until cheese is heated through.