Preheat the oven to 350°F (177°C). Line an 8×8 pan with parchment paper along the bottom and two sides.

Mash the bananas until mostly smooth with few lumps. Measure out ⅔ cup of mashed banana.

In a heat-safe bowl, add the unsalted butter and semi-sweet chocolate chips. Heat until fully melted and combined, either using a “bain marie” or in the microwave (30 seconds at a time, stirring in between).

Stir in the granulated sugar just to combine, then return the bowl to the microwave for another 30 seconds. Stir until the sugar is fully incorporated, and allow the mixture to cool for 5 minutes.

Whisk in the eggs, mashed bananas, vanilla extract, cocoa powder, and salt until smooth and glossy. The batter should fall like a ribbon when lifted with a spatula.

Stir in the flour until well combined, then fold in the additional chocolate chips.

Pour the batter into the prepared pan and bake for 30-40 minutes. Start checking at 30 minutes with a toothpick. If the toothpick comes out with moist crumbs, it’s done. If it comes out wet, bake for another 5-10 minutes.

Allow the brownies to cool at room temperature for at least one hour, then refrigerate for another hour to fully set.

Once cooled, remove from the pan using the parchment paper overhang, slice, and serve.