1. Preheat the oven to 220°C. Grease or flour a baking tray.
2. Sift the flour, baking powder and salt into a bowl. Add cheese, cayenne pepper and mustard powder to the mixture. Rub in the butter with your fingertips until the mixture resembles fine breadcrumbs.
3. Add the milk and quickly mix with a round-bladed table knife to a soft dough. For light and tender scones the mixture should be quite soft and a little sticky. Scrape the dough onto the floured baking tray and flour the top.
4. Working quickly, pat the dough out to 2cm thickness. With a floured knife, cut it into 12 even-sized pieces, then separate the scones to allow 2cm space between them. Brush the tops with milk.
5. Before baking, top each scone with a little more grated cheese. Bake for 10 minutes or until golden brown. Place on a wire rack to cool, wrapped in a clean tea towel to keep them soft.