Preheat the oven to 180°C/160°C fan/Gas 4. Grease a 30 x 23-cm/12 x 1-inch bread tin.
Pour the mashed bananas into a big mixing bowl. Mix in the butter, sugar, egg, 25g of walnuts and vanilla extract. Add the bicarbonate/baking soda and salt and mix in the flour last. Optional: Add 25g milk chocolate chips to mix for a sweet treat.
Pour into the prepared tin. Top with 25g of walnuts and sprinkle with sugar. Bake for 50 minutes to an 1 hour, remove and cool,
