Preheat oven to 180 C / Gas 4. Grease one 23x33cm or similar sized baking dish.
Stir together the pumpkin, banana, egg and egg whites in a large bowl. Beat in maple syrup, sugar and vanilla; the batter should be a bit frothy. Stir in courgette; set aside.
Mix flour, wheat bran, salt, bicarbonate of soda, baking powder, cinnamon, nutmeg, cloves, ginger and allspice in a separate bowl. Gradually add the flour mixture to the courgette mixture, stirring just to moisten all ingredients. Over-mixing the batter will make it tough.
Pour the batter into the prepared dish. Bake until a skewer inserted in the centre comes out clean, 50 to 60 minutes. Cool completely before cutting into squares.
Pumpkin puree can be purchased online. If unavailable, substitute in unsweetened apple sauce.
Wheat bran can be purchased in health stores or online.
You can also use this recipe to make muffins. Adjust the baking time accordingly.