Pre-heat oven to Gas 7 (425°F/220°C). Put the grated cheese into a mixing bowl. Weigh out the flour and sieve it with the baking powder and spice into the cheese. Cut the butter into small pieces and rub into the flour and cheese with your fingers. Add the egg yolks and mix with a wooden spoon into a stiff dough. Gather into a ball, press out with your hands on to a floured board and then roll to about ½ in (1 cm) thick. Cut into straws with a sharp knife and place carefully on a large ungreased baking sheet. Bake in the top part of the oven for 8–12 minutes until just golden brown. Cool and then remove carefully from the baking sheet.