Sift the flours and salt together, add the egg, lightly beaten, and gradually beat in the liquid until smooth. Stir in the potato.
Pour into a greased square cake tin or roasting pan, and bake at about 190°C/375°F/gas mark 5 for 20 minutes or so, until the mixture is brown on top.
Turn out, allow to cool a little, and cut into squares to serve.
© 2000 Frances Bissell. All rights reserved.