First, you'll need to boil or bake the sweet potatoes to soften them. It doesn't matter which methods but be sure to leave the skin on for both. Boiling can take up to 40 minutes or until you can easily pierce them with a knife. Bake at 400℉ for 45-60 depending on the sizes of the sweet potatoes.
Preheat the oven to 400℉.
In a bowl combine the dry ingredients together. Mix the cornmeal, flour, sugar, baking powder and the spices together.
Using a hand mixer, blend the softened sweet potatoes with the eggs, milk, oil and yogurt or sour cream.
Now, fold in the dry and wet ingredients until everything is even and smooth. Grease a 9x9 baking dish then bake for 35-40 minutes or until the center is fully cooked, do not allow the edges to fool you.
Once finished allow to cool before serving.