Line a large baking sheets with parchment paper or a non-stick sheet. In a large bowl, stir together the flour, sugar, baking powder, salt, and pepper. Using a pastry cutter or your hands, cut in the shortening until the mixture has small, pea-sized chunks of shortening throughout. Toss in the chopped Serranos and shredded cheddar cheese until everything is well coated in flour. Stir in the buttermilk until the dough begins to form.