Preheat the oven to 425°F. Place 2 tablespoons of solid vegetable shortening into the cast iron skillet and set it into the oven to preheat and melt the shortening.
In a medium mixing bowl, sift together the dry ingredients.
In a separate bowl, whisk together 1 3/4 cups of buttermilk, 1/4 cup of vegetable oil, and 2 eggs until combined.
Add the wet ingredients to the dry ingredients and mix together until all of the dry ingredients are fully moistened.
Next, add 1 cup of small diced cooked ham, 1 cup of shredded sharp cheddar cheese, 1 cup of corn and green onions to the batter. Mix well.
Remove the skillet from the oven and swirl the melted shortening around the pan coating the bottom and sides completely. Discard any excess.
Pour the batter into the hot skillet and spread evenly. Sprinkle the remaining cheddar cheese on top.
Place into the oven and bake for 25-30 minutes or until a toothpick inserted into the middle comes out clean.
Rest for 5 minutes before cutting and serving.
The process of preheating the cast iron skillet gives the cornbread an incredibly crunchy and delicious crust. If you don't have a cast iron skillet, you can use a square 8x8 inch baking dish or a deep dish 9 inch pie plate.