Preheat the oven to 200˚C (fan) or 220˚C / 392˚F (convection).

Line a baking tray with baking parchment.

In a large mixing bowl, combine the plain flour and baking powder.

Cut cold, cubed butter into the flour mixture until it resembles coarse breadcrumbs.

Stir in the grated cheddar cheese.

In a separate bowl, mix together cold milk, cold water, and Dijon mustard. Pour into the flour mixture and stir gently.

Turn the dough onto a floured surface, knead gently, and roll to a thickness of 3 cm (1.2 inches).

Cut out rounds from the dough using a round cutter and place on the prepared tray.

Sprinkle extra grated cheese on top if desired.

Bake for 12-15 minutes or until golden brown on top.

Allow to cool on a wire rack for a few minutes before serving.