1.Preheat oven to 240ºC (220ºC fan forced). Grease a deep 19cm square cake pan. Sift flour into a large bowl, rub in butter. Stir in lightly beaten egg, grated smoked cheddar, mustard and about ¼ cup (60ml) milk to make a soft, sticky dough.
2.Turn dough onto a floured surface, knead gently until smooth. Press dough out evenly into a 2cm thickness. Use a 5cm round cutter to cut rounds from dough, place side by side, just touching, in pan. Gently knead dough scraps together repeat pressing and cutting out scones.
3.Bake scones about 15 minutes.