Stir together flour, baking powder, salt, pepper and sugar in a large bowl. Gradually cut in the butter with a pastry blender or two knives until the mixture resembles small peas. Stir in the cheese, just until combined. Add green onions, jalapeños, bacon, and 1/3 cup buttermilk. Mix by hand just until all the ingredients are incorporated. If the dough is too dry to hold together, use remaining buttermilk, adding 1 tablespoon at a time, until dough is pliable and can be formed into a ball. Mix as lightly and as little as possible to ensure a light-textured scone.
Place dough on a lightly floured board. Pat dough into a ball. Using a well-floured rolling pin, flatten dough into a circle about 7 inches wide and 1/2 inch thick. Cut into 8 equal wedges.
Whisk egg and milk together in a small bowl and brush tops of each scone.
Place scones on an ungreased baking sheet and bake 18 to 20 minutes, until golden brown and no longer sticky in the middle. Serve warm.