In a large bowl, whisk together flour, baking powder, salt, sugar, black pepper, and red pepper. Using 2 forks or a pastry blender, cut butter into flour mixture until crumbly. Make a well in dry ingredients; add cheeses and ¾ cup buttermilk, stirring until mixture just comes together. Add remaining ¼ cup buttermilk, if needed.
On a lightly floured surface, gently knead dough 4 or 5 times. Roll or pat dough into an 8-inch square; cut into 25 squares. Place close together in a 10-inch square cast-iron skillet or a parchment-lined baking sheet.
Bake until golden brown, about 17 minutes. Let cool for 15 minutes. Using a large spatula, remove from pan, and cut into pieces. Split biscuits horizontally, and brush with melted butter. Serve with mustard and ham, if desired.
Recipe by The Ribbon in My Journal - Phyllis Hoffman DePiano at https://www.theribboninmyjournal.com/lets-talk-biscuits/