Sift the flours, baking powder, bicarbonate of soda and salt into a large bowl, tipping in the wheatgerm left in the sieve. Stir in the sugar. Mix together the bananas, egg, measurement water and oil in a jug. Add to the dry ingredients and stir together using a large metal spoon until just combined. Fold in the carob or chocolate.
Divide the mixture evenly between ramekins or paper muffin cases arranged in a 12-hole muffin tray. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes until they are well risen and spring back when pressed. Transfer to a wire rack to cool.