Preheat your oven to 180°C (350°F) and line a muffin tin with paper liners or lightly grease it.
Peel the bananas and mash them thoroughly in a large mixing bowl with a fork or potato masher until smooth and jammy, with some small lumps remaining for texture.
Chop the dark chocolate into small chunks or melt it in short bursts in the microwave, stirring until smooth. Let it cool slightly.
Add the brown sugar to the mashed bananas and stir well to combine. Then, whisk in the eggs one at a time until the mixture is shiny and cohesive.
Pour in the vegetable oil and mix until fully incorporated, creating a glossy batter that smells sweet and chocolatey.
In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt to ensure an even distribution of dry ingredients.
Gradually fold the dry ingredients into the banana mixture, mixing gently until just combined—don’t overmix or the muffins could turn dense.
Stir in the melted or chopped chocolate and chocolate chips, distributing evenly throughout the batter.
Spoon the batter into the prepared muffin cups, filling each about three-quarters full for a rounded top.
Bake in the preheated oven for 20–22 minutes, until the tops crack slightly and a toothpick inserted into the center comes out with moist crumbs.
Remove the muffins from the oven and let them cool in the tin for 5–10 minutes, then transfer to a wire rack to cool completely for best texture.
Enjoy these warm or at room temperature, perhaps with a glass of milk or a dollop of yogurt for extra indulgence.
