Preheat the oven to 350°F (175°C). Grease or line a 9x5-inch loaf pan with parchment paper.In a large mixing bowl, mash the ripe bananas until mostly smooth.Whisk in the melted butter, granulated sugar, brown sugar, eggs, and vanilla extract until well combined.Add the flour, baking soda, salt, and cinnamon. Stir gently until just combined.Fold in the chopped walnuts or chocolate chips if using.Pour the batter into the prepared loaf pan and smooth the top.Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.Let the bread cool in the pan for 10 minutes, then transfer it to a wire rack to cool for another 10 minutes before slicing.
