This is an adaptation of my Mexican Cornbread Casserole and Broccoli Cornbread. I usually use 1 pkg buttermilk cornbread mix and 1 pkg Mexican cornbread mix. You can use Jiffy Mix if you like sweet cornbread. Warning: This is not a light fluffy cornbread. The texture will be much more dense.
Preheat oven to 375 degrees. Place butter in a 10 inch cast iron skillet and then in oven to melt and heat the skillet.
Mix all other ingredients together. Batter should be slightly thick, but if you think it is too thick add a few tablespoons milk or water.
After butter is melted and skillet is hot, take the skillet out of the oven, pour most of the melted butter into the batter and stir. (If you get the skillet really hot, it will make a nice crispy crust on the bread.)
Pour the batter back into the skillet and return skillet to the oven. Bake until golden on top. About 25 or 30 minutes.