Fit the double-bladed knife.
Put all the ingredients into the bowl and process for 10 - 15 seconds or until the mixture forms a dough ball.
If the dough is too soft to handle chill slightly, than press into a greased 7 x 10” (18 x 25 cm) swiss roll tin.
Prick all over the surface with a fork and bake in a moderate oven 160° C (gas mark 2/3) for 30 - 35 minutes or until pale golden in colour.
Cut the shortbread into fingers, allow to cool slightly in the tin, then remove to cool completely on a wire rack.