Preheat the oven to 175 °C (325 °F)
Beat the sugar and eggs until well incorporated.
Beat in the banana.
Add flour, baking powder, bicarbonate of soda, cinnamon and ginger to the sugar mixture.
Mix thoroughly until all the dry ingredients have been incorporated into the wet mixture.
Pour in the melted butter (let it cool down a little bit) and beat until all the ingredients are well mixed.
Add your chocolate chips and mix them in.
Pour the mixture into the prepared loaf tin (greased and dusted with flour).
For the topping: Melt the butter in a little pan, add walnuts and maple syrup.
Let it simmer for 2 minutes.
Spoon the topping on top of the banana bread.
Bake in the preheated oven for about 1 hour, or until a skewer comes out clean.