Method: melt margarine and add sugar and oil. Add buttermilk and eggs. Mix in wholewheat flour, and then add flour and baking powder in stages. Finally, add the bran.
Bake at 180°C for 50 minutes. Cut into 4x4 squares and dry these at 70-90°C for 4 hours, allowing them to cool completely after 2 hours.
Recommended variation: add sunflower seeds, raisins, or almonds when adding the bran.