Preheat oven to 400°F (200°C).

In a large bowl, combine cornmeal mix and baking soda.

Add creamed corn, chopped onion, and chopped jalapeno peppers.

Stir in grated Cheddar cheese, reserving 1/2 cup for topping.

In a separate bowl, whisk together cooking oil, buttermilk, and beaten eggs.

Pour the wet ingredients into the dry ingredients and mix until just combined.

Heat a skillet (preferably cast iron) over medium heat.

Pour the cornbread mixture into the hot skillet.

Sprinkle the remaining Cheddar cheese over the top.

Bake in the preheated oven for 40 minutes, or until golden brown and a toothpick inserted into the center comes out clean.

Let cool slightly before serving.