Cream butter and brown sugar together in a bowl. Add 375g (3 cups) to 470g (3¾ cups) flour. Mix well.
Sprinkle board with the remaining flour. Knead mixture for 5 minutes, adding enough flour to make a soft dough. Roll to 1cm thickness. Cut into 8cm x 2.5 cm strips. Prick with a fork and place on ungreased baking trays.