Prep the pan and oven. Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.

Mash the bananas. In a large bowl, mash the bananas with a fork until mostly smooth with a few small lumps. You want about 1 1/3 cups.

Whisk the wet ingredients. Add brown sugar, granulated sugar, eggs, melted butter, oil, yogurt, and vanilla to the bananas. Whisk until combined and glossy.

Combine the dry ingredients. In a separate bowl, whisk together flour, cocoa powder, baking soda, salt, and cinnamon until evenly mixed and lump-free.

Bring it together. Sprinkle the dry mixture over the wet mixture. Fold gently with a spatula just until you no longer see dry streaks. Do not overmix.

Stir in add-ins. Fold in chocolate chips and nuts if using. The batter will be thick and luscious.

Fill the pan. Scrape the batter into the prepared loaf pan and smooth the top. For a bakery-style look, sprinkle a few extra chips or a pinch of coarse sugar on top.

Bake. Bake for 55–70 minutes, until the top is set and a toothpick inserted in the center comes out with a few moist crumbs (melted chocolate is fine, but no wet batter).

Cool properly. Let the loaf cool in the pan for 15 minutes, then lift it out and cool completely on a wire rack before slicing. This helps the crumb set and stay moist.