Preheat your oven to 375°F (190°C). Gather all your ingredients.

Melt the unsalted butter in a medium saucepan over low heat, then mix in the espresso powder until dissolved.

Mash the ripe bananas in a mixing bowl until mostly smooth, leaving some chunks for texture.

Pour the melted butter and espresso mixture into the bowl with the mashed bananas and stir until creamy.

Add both granulated and brown sugar to the banana mixture and mix until well incorporated.

Crack an egg into the mixture, stir until just combined.

Sift together all-purpose flour, baking soda, and kosher salt into the banana mixture, gently folding in.

Fold in the semi-sweet chocolate pieces until evenly distributed.

Prepare your loaf pan by greasing it or lining it with parchment paper.

Pour the batter into the prepared loaf pan and smooth the top. Bake for approximately 40-45 minutes.

Let the loaf cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

Once cooled, slice the banana bread and serve warm, optionally with coffee butter.