Start by preheating your oven to 180°C (356°F). While it heats, line a loaf pan or small baking dish with parchment paper. Don't skip the parchment—it makes removing the cake infinitely easier and keeps those beautiful blueberries intact on top.

In a large mixing bowl, take two of your bananas and mash them thoroughly with a fork until completely smooth with no visible chunks. The smoother your mash, the more uniform your cake texture will be.

Add the two eggs and whisk them into the mashed bananas until fully combined and slightly frothy.

Add your oats, cocoa powder, and baking powder to the bowl. Pour in the milk and unsweetened yogurt. Stir everything together until no dry flour remains, but be careful not to overmix—you want a cohesive batter, not a workout for your arm muscles.

Finally, fold in the chopped dark chocolate pieces, distributing them evenly throughout the batter.

Pour exactly half of your prepared batter into the parchment-lined pan and spread it evenly to the edges.

Take your remaining whole banana and gently place it lengthwise right down the center of the batter—this will become the glorious hidden pocket of sweetness.

Slowly and carefully pour the remaining batter over the banana, trying to keep it centered. Use a spatula to gently smooth the top.

Now for the fun part. Sprinkle the surface generously with your heat-resistant chocolate chips, pressing them in just slightly so they stick.

Arrange fresh blueberries artfully across the top—they'll bake into jewel-like bursts of color and flavor.

Place your pan in the preheated oven and bake for 30 minutes. You'll know it's done when the top is set and firm to a gentle touch, and your kitchen smells like the world's best chocolate bakery. A toothpick inserted in the center (avoiding the whole banana pocket) should come out with just a few moist crumbs.

Let the cake cool in the pan for about 10 minutes, then use the parchment to lift it onto a cooling rack. While still warm, arrange a few more fresh blueberries on top for that just-made look, and drizzle with chocolate sauce in a zigzag pattern. The warm cake will slightly melt the sauce, creating a gorgeous glossy finish.

This cake can be stored covered in the refrigerator for 2-3 days. It actually improves after a day in the fridge—the flavors meld and the texture becomes even more satisfyingly dense. Serve at room temperature or slightly warmed for the best experience.