Preheat the oven to 350°F (175°C) and line a large loaf pan with parchment paper.

In a mixing bowl, combine slightly melted peanut butter, granulated sugar, and mashed bananas. Add vegetable oil and eggs and whisk until smooth.

Introduce cocoa powder, baking soda, salt, and vanilla extract to the mixture. Stir until fully combined.

Gradually fold in all-purpose flour until just combined, being careful not to overmix.

Pour the batter into the prepared loaf pan. Optionally, add sliced bananas on top.

Bake for approximately 55 minutes or until a toothpick inserted comes out clean.

Let the loaf cool in the pan for 20 minutes before transferring to a wire rack.

Drizzle warm melted peanut butter over the top before slicing and serving.