Step 1

Preheat oven to 160C. Grease a 12.5cm x 25.5cm loaf pan (2.25-litre/9-cup capacity); line base and long sides with baking paper, extending the paper 5cm over the sides.

Step 2

Mash 4 of the bananas in a medium bowl; you will need 1 cup mashed banana. Add melted butter, brown sugar, golden syrup, egg and vanilla to the mashed banana. Using a wire whisk, stir until combined. Fold in combined sifted flours and cinnamon. Stir in milk and walnuts until well combined. Spoon mixture into pan; smooth the surface.

Step 3

Place demerara sugar on a plate. Cut remaining banana in half lengthways; coat in sugar. Place banana, cut-side-up, on mixture; sprinkle with remaining sugar from plate.

Step 4

Bake for 1 hour (cover loosely with foil if it starts to overbrown) or until a skewer inserted into the centre comes out clean. Leave in pan for 10 minutes then transfer to a wire rack to cool.

Step 5

Combine extra golden syrup and 2 tsp boiling water in a small bowl; brush over top of loaf. Serve sliced with butter.