Preheat oven to 400°.
Mix cornmeal, flour, baking soda, and salt in a bowl and set aside.
Mince the jalapeño and set aside.
Melt butter and add to a mixer bowl.
Add sugars to butter and mix.
Quickly beat eggs into the butter mixture.
Mix in buttermilk.
Slowly mix in flour mixture, until just mixed.
Fold in the minced jalapeño.
Add bacon grease to a 10in cast iron pan and place in oven until melted.
Pour batter into cast iron pan and bake for 20-25 minutes.