01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, baking powder, salt, black pepper, and dry mustard powder.
03 - Add cold cubed butter and rub in with fingertips until mixture resembles coarse breadcrumbs.
04 - Stir in grated cheddar cheese and finely chopped chives or spring onions if using.
05 - Whisk together milk and egg in a small bowl; reserve 1 tablespoon for brushing.
06 - Pour remaining milk and egg mixture into dry ingredients, mixing gently with a fork until just combined, avoiding overworking.
07 - Turn dough onto a floured surface and gently pat into a round approximately ¾ inch thick.
08 - Use a 2-inch round cutter to cut out scones, re-rolling scraps as necessary. Arrange scones on prepared baking sheet.
09 - Brush scone tops with reserved milk and egg mixture.
10 - Bake in preheated oven for 12 to 15 minutes until risen and golden brown.
11 - Allow scones to cool slightly on a wire rack. Serve warm with butter if desired.