Preheat oven to 350° F. Spray a 9 x 5-inch loaf pan with baking spray (I used coconut oil spray) or grease with butter. Lay a sheet of parchment paper across the bottom and up the two long sides of the pan.
In a large mixing bowl, combine the melted butter, mashed banana and brown sugar. Whisk until well combined. Whisk in the eggs.
⅓ cup (76g) unsalted butter, 1 ½ cups (380g) mashed ripe banana, ½ cup (100g) light brown sugar, 2 large eggs
Add the baking soda, vanilla, cinnamon and salt to the bowl and whisk until very well combined.
1 teaspoon baking soda, 1 teaspoon vanilla extract, ½ teaspoon ground cinnamon, ½ teaspoon salt
Add the flour and stir with a rubber spatula until just combined. Do not over-mix the batter. Then gently stir in the chocolate chips until just combined. Pour the batter into the prepared baking pan. Sprinkle a few more chocolate chips over the top of the batter and slightly press them down into the top of the batter.
1 ¾ cups (210g) all-purpose flour, ¾ cup (135g) chocolate chips
Bake for 55-65 minutes, until a tester inserted in the center comes out clean or with just a few moist crumbs. Check on the loaf after 35 or 40 minutes and if the top is browning too much, loosely tent with foil. (Fold a square of foil in half to crease it, then lay it loosely on top of the baking bread like a tent.)
Let the bread cool in the pan for 15 minutes and then remove to a wire rack to finish cooling.