125 g (4 oz) self-raising flour, plus extra for dusting
1/2 teaspoon dry mustard powder
pinch of salt
1 teaspoon cracked black pepper
50 g (2 oz) unsalted butter, softened
25 g (1 oz) mature Cheddar cheese, finely grated
1 large egg yolk
1 tablespoon water
Line 2 baking sheets with nonstick baking paper. Mix together the flour, mustard powder, salt and black pepper in a bowl. Add the butter and rub in with the fingertips until the mixture resembles fine breadcrumbs. Stir in the cheese, then add the egg yolk and measurement water and mix to form a firm dough.
Turn the dough out on to a floured surface and knead lightly. Roll out to 2–3 mm (1/ 8 inch) thick, then stamp out 20–22 rounds or shapes using a 5 cm (2 inch) cutter.
Place the rounds on the prepared baking sheets and bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 10 minutes, or until lightly golden. Transfer to wire racks to cool.