Preheat the oven temperature to 450 degrees F.
Place the bacon grease in a 10-inch black cast-iron skillet and swirl to coat the sides and bottom evenly. Place skillet in the oven to heat.
In a bowl, combine the cornmeal, baking powder, baking soda, salt, and pepper and mix well.
In another small bowl combine the buttermilk, egg, melted butter, jalapenos, and mashed roasted garlic. Add to dry ingredients and stir to combine.
Remove the hot skillet from the oven and carefully swirl to evenly distribute the hot grease. Quickly pour the cornmeal batter into the skillet and bake until firm and golden brown on top, 25 to 30 minutes. Let sit for 5 minutes, then turn out onto a cutting board. Cut into wedges and serve hot, with butter on the side.