Preheat your oven to 220°C (425°F). Position your oven rack in the middle for even baking.
Line a baking sheet with parchment paper or a silicone baking mat.
In a large mixing bowl, sift together 250g self-raising flour, 1 tsp baking powder, ¼ tsp salt, and a pinch of cayenne pepper. If using mustard powder, sift it into the mixture for an extra hint of warmth and depth.
Add 75g of cold, cubed butter to the dry ingredients. Use a pastry blender, a fork, or your fingertips to work the butter into the flour mixture until it resembles coarse crumbs. Stir 150g of grated cheddar cheese into the crumbly flour mixture.
In a separate bowl, whisk together 125ml of milk and 1 large egg. Make a well in the centre of the dry ingredients and pour in the wet mixture.
Mix until just combined to form a sticky dough. Be careful not to overmix, as this will make the scones tough.
Turn the dough onto a lightly floured surface and knead gently a few times.
Shape the dough into a round disc about 2 cm thick. Use a round cookie cutter to cut out 8 scones, or simply cut the disc into 8 wedges.
Place the cut scones on the prepared baking sheet.
Optional: Brush the tops with a little milk for a shiny finish.
Bake for 15-20 minutes, or until the scones are golden brown on top. Remove from the oven and transfer to a wire rack to cool slightly.
