Start by preheating the oven to 180°C (350°F).
Then, grease and line a standard loaf pan or 1lb loaf tin.
In a large bowl, mash the bananas with a fork or whisk until mostly smooth.
Then, crack in the eggs one at a time and whisk together well for a few minutes.
Next, add the sugar and melted butter, mix well to combine, and set aside.
In a small bowl, combine 20ml of warm water with the instant espresso or instant coffee powder and mix well.
Now, add the salt, vanilla and coffee mixture to the banana mixture and whisk well to combine.
Sift in the plain flour and baking powder, then mix well to combine (but do not overmix!).
In a separate medium bowl, coat the chocolate chips and chopped walnuts in 1 tbsp of flour, then fold them into the banana bread mixture.
Pour the banana bread batter into the prepared loaf pan and top with the extra chocolate chips, walnuts and a sprinkle of granulated sugar for that extra-crispy top.
Place in the preheated oven and bake for 40–50 minutes, until the top is golden and a toothpick inserted into the centre comes out clean or with a few moist crumbs. Note: The top of the banana bread often browns before the inside is fully cooked, so once the top has browned, cover the loaf pan with a sheet of foil and continue baking until the centre is fully cooked. When the banana bread is fully cooked, allow it to cool completely on a wire rack.
Once fully cooled, slice, serve and enjoy!