Preheat the oven to 220 degrees C or gas mark 7; Line a baking tray with parchment.
1. Sift together the flour, baking powder and seasoning into a medium sized mixing bowl. Rub in the butter then stir in the cheese, reserving a little to sprinkle on the tops.
2. Beat together the egg, milk and mustard. Add the liquid a little at a time to the flour, mixing to a firm dough. Reserve a little of the liquid to brush on the tops.
3. Roll out to about 1.5 cm thick and, using a plain cutter, cut into rounds.
4. place on the baking tray, brush with the egg mixture and sprinkle with cheese. bake for about 10 -15 minutes until golden brown.