One more point: there is a difference between a sweet potato and a yam. Most people use the terms interchangeably and most recipes can handle either. You can use either for this recipe. I find that most stores carry yams year round, but sweet potatoes only seasonally. Both are good and Yams have more orange in them which usually is a sign of really good vitamins and antioxidants and other really positive things.
Now that we know how good they are, lets add naughty things. The main thing we are adding here are apples, which aren't naughty so that is a good sign. They sweeten up the potatoes quite a bit. The only key is that, depending on how you like the texture, the potatoes will probably need more cooking time than the apples. Cut them both the same size. This recipe serves 12, I have cut it in half many times. While typing this in, I also was thinking that you could toss some nuts into it as well. I haven't tried it yet.
6 sweet potatoes OR yams (cooked, peeled, and cubed)
6 tart apples (peeled, cored, and cubed)
3/4 cup brown sugar
1 tsp cinnamon
1/4 tsp nutmeg (optional)
1/2 tsp salt
1 Tbsp melted butter
1 Tbsp lemon juice
Preheat oven to 350. Place cooked potatoes and uncooked apples in a 9x13 inch baking dish. Combine the remaining ingredients and mix together in a separate bowl. Toss with potatoes and apples. Bake for 1 hour.