Preheat your oven to 425°F (220°C) and place a cast iron skillet inside to heat up. Allow the skillet to warm for at least 10 minutes while you prepare the biscuit dough.

In a large mixing bowl, whisk together the dry ingredients: all-purpose flour, baking powder, salt, and black pepper.

Add the cold butter, cut into small cubes, to the flour mixture. Use a pastry cutter or your fingers to work the butter into the mixture until it resembles coarse crumbs.

In a separate bowl, whisk together the egg and buttermilk. Add in the diced jalapeños and shredded cheddar cheese, then stir to incorporate.

Make a well in the center of your dry ingredients and pour in the wet mixture. Gently combine until just incorporated.

On a lightly floured surface, turn out the dough and gently press it into a rectangle, folding it over itself a few times.

Using a biscuit cutter or a sharp knife, cut out rounds or squares of dough and place each biscuit into the preheated cast iron skillet.

Brush the tops with buttermilk and bake for 20-25 minutes until golden brown.

Once baked, remove from the oven and brush the tops with melted butter, optionally sprinkling with flaky sea salt.