Preheat the oven to 350°F (176°C). Lightly butter the sides and bottom of a 9×5-inch loaf pan to help the parchment paper adhere, then line with a strip of parchment paper.

In a large bowl, whisk together the mashed bananas, melted butter, brown sugar, granulated sugar, egg, egg yolk, and vanilla until glossy.

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

Gently fold the dry ingredients into the wet ingredients just until combined – do not overmix.

Fold in 3⁄4 cup of the chocolate chips.

Pour the batter into the prepared loaf pan, gently tap the pan on the counter to level the batter, then sprinkle the remaining 1⁄4 cup of chocolate chips evenly over the top.

Bake for 60–70 minutes, until a toothpick inserted into the center comes out mostly clean with no wet batter. Melted chocolate is normal.

Let cool in the pan for 10–15 minutes to set, then lift out using the parchment overhang and cool completely on a wire rack to prevent sogginess.

Once cooled, slice into 8 thick pieces.

Please note: For a slightly firmer loaf, use 1-1⁄4 cups mashed banana. For a denser, moister banana bread, use 1-1/2 cups mashed banana.