Preheat oven to 350°F (175°C) and line a 9x5 inch loaf pan with parchment paper.

In a large bowl, whisk together mashed bananas, Greek yogurt, eggs, maple syrup, and vanilla extract until homogenous.

In a separate bowl, sift together oat flour, protein powder, baking powder, baking soda, salt, and cinnamon.

Gradually fold the dry ingredients into the wet mixture using a spatula until just combined, ensuring no flour pockets remain.

Fold in 2 tablespoons of dark chocolate chips into the batter.

Pour half of the batter into the prepared loaf pan and spread evenly.

Warm the peanut butter slightly and drizzle it over the bottom layer of batter, then swirl with a knife.

Pour the remaining batter over the peanut butter layer and smooth the top.

Sprinkle the remaining dark chocolate chips across the surface of the loaf.

Bake for 45 to 55 minutes, or until a toothpick inserted into the center comes out clean.

Cool in the pan for 10 minutes before removing to a wire rack to cool completely before slicing.