I had forgotten how good these were! My mother's recipe, so Imperial measurements, but have made an approximate translation.
8 oz (250 g) self-raising flour
1 1/2 oz butter (45 g)
4 oz strong Cheddar or other cheese (124 g)
3/4 tsp baking powder.
1/2 tsp each cayenne pepper and dry mustard powder
Scant 1/4 pint milk (c 125 ml)
Grate cheese. Rub butter into flour and seasonings, mix in cheese and add sufficient milk to make dough. Roll out to about 1 cm thick, put on greased baking sheet, brush with milk and score into 6-8 pieces. Bake in hot oven (Mark 7) for 15-20 minutes. Let cool, split, butter and eat, preferably while still warm.