Preheat your oven to 350°F (175°C) and grease a loaf pan. You can also line it with parchment paper for easier removal.
In a large mixing bowl, cream together the softened butter and brown sugar until light and fluffy. This should take about 3-5 minutes.
Add the eggs, one at a time, mixing well after each addition. Then, stir in the vanilla extract until fully incorporated.
Add the mashed bananas and powdered peanut butter to the mixture. Stir until combined and smooth.
In a separate bowl, whisk together the light spelt flour, baking powder, bicarbonate of soda, cocoa powder, and any additional sugar you choose to use.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. If the batter is too thick, add warm water, one tablespoon at a time, until you reach your desired consistency.
Gently fold in the dark chocolate chips, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, cover it loosely with aluminum foil.
Once baked, remove the loaf from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely before slicing. Enjoy your Peanut Butter Chocolate Chip Banana Bread warm or at room temperature!