Heat the oven to 400F. Place dry cast iron skillet in the oven while it is heating until you are ready to pour ingredients in.
Mix the cornbread according to package directions. Stir thoroughly.
As soon as the pan is out of the oven, add the bacon grease to the bottom.
Working quickly, line the bottom of the pan with the jalapenos.
Sprinkle the grated cheese over the jalapenos.
Pour the cornbread on top. Sprinkle the top with a light layer of kosher salt.
Bake according to package instructions.