Coat the inside of a 10-inch cast iron skillet with oil or cooking spray. Place the skillet in the oven and begin to preheat the oven to 425 degrees Fahrenheit.
Stir together the cornmeal, flour, sugar, baking powder, salt, ground cinnamon and pumpkin pie spice (or nutmeg) in a large bowl.
In a separate large bowl, whisk together the mashed sweet potatoes, eggs, sour cream, milk and 2 tablespoons of oil until smooth.
Stir the wet ingredients into the dry ingredients and mix until just combined.
Carefully, remove the hot skillet from the heated oven. Pour the batter into the hot skillet and smooth out the top with a spatula.
Return the skillet to the oven and bake for about 20 to 25 minutes or until the center is completely set and the top is golden brown.
Remove the cornbread from the oven and let it cool for about 5 minutes. Serve with butter and honey (optional).