Add the flour, baking powder, and salt to a large mixing bowl. Stir to combine.
Add the cubed butter and using a pastry blender, cut the butter into the dry ingredients until it resembles coarse crumbs. Alternatively, start with frozen butter and use a cheese grater to grate it into the dry ingredients.
Add the shredded cheese and chives and stir to combine.
Combine the beaten egg and milk and pour into the dry ingredients. Stir gently just until the mixture comes together.
Turn the dough out onto a lightly floured countertop or a large piece of parchment paper. Bring the dough together with your hands, then lightly flour the top of the dough. Roll the dough until it is about 1/2 inch thick. Fold the dough in half and roll again to 1/2 inch thick. Repeat one more time. (If you don't have a rolling pin you can press it out with your hands)
Cut dough into rounds with a 2.5 or 3-inch biscuit or cookie cutter, pressing straight down. Gather the scraps and roll again repeating the process until you have used all the dough. Place the biscuits on a parchment-lined baking sheet, leaving about 1/4-inch space between biscuits.
Place into the oven and bake for 15-18 minutes until biscuits have risen and are golden brown.
Notes
For best results, we recommend weighing the ingredients.
Freshly shredded cheese will produce better results than store-bought pre-shredded cheese.