01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, whisk together all-purpose flour, baking powder, baking soda, and salt until well blended.
03 - Add cold cubed butter to the flour mixture. Using a pastry cutter or fingertips, cut butter into flour until the mixture forms coarse crumbs.
04 - Add grated cheddar cheese and finely diced jalapeños; stir until evenly distributed.
05 - Pour cold buttermilk into the bowl. Gently mix with a fork until the dough comes together. Avoid overworking.
06 - Transfer dough to a lightly floured surface. Pat the dough into a 1-inch thick rectangle. Use a 2.5-inch round cutter to cut out biscuits, gathering and re-pressing scraps as necessary.
07 - Place biscuits 1 inch apart on the prepared baking sheet.
08 - Bake for 16 to 18 minutes, until biscuits are golden and well risen.
09 - Allow biscuits to cool briefly before serving warm.