Melt the butter and set aside. Mash the bananas with a fork, then pour in the melted butter. Stir to combine.
Always mixing with a fork, add the baking powder and the sugar to the banana mash. Lightly whisk an egg aside, then add it to the banana mixture and stir to combine.
Fold in the flour, adding it in two batches. Lastly, fold in 2/3 of the chocolate chips.
Transfer mixture into a loaf pan that has been previously greased. Sprinkle the remaining chocolate chips over the top of the cake.
Bake in the preheated oven at 175°C for about 1 hour, or until a toothpick inserted in the centre comes out clean. If the top of the banana bread is getting too brown after 40 minutes, switch the settings of the oven so that the heat only comes from the bottom for the last part of the baking time.