Preheat the oven to 350°F (175°C). Line a muffin tin with paper liners or grease it well.

In a large mixing bowl, mash the bananas until smooth. Add the eggs, brown sugar (or honey), vegetable oil (or melted butter), and vanilla extract. Whisk until fully combined.

In a separate bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix.

Fold in the dark chocolate chips or chunks.

Divide the batter evenly among the muffin liners, filling each about ¾ full. For bakery-style muffin tops, fill them nearly to the top and bake at 375°F (190°C) for the first 5 minutes, then lower the temperature to 350°F (175°C).

Bake for 18-22 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (but no wet batter).

Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely before serving.