Preheat oven to 350°F. Grease or line a 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal.

Mix wet ingredients – In a large bowl, whisk together melted butter and brown sugar until smooth. Beat in the egg, vanilla, and mashed bananas until combined.

Add dry ingredients – Sprinkle flour, baking soda, and salt over the wet mixture. Gently fold until just combined—do not overmix.

Fold in most of the chocolate chips, reserving a handful to sprinkle on top.

Spread batter evenly in prepared pan. Sprinkle remaining chocolate chips over the top. Bake 35-45 minutes, or until the center is set and a toothpick comes out with just a few moist crumbs (not wet batter). If you notice the bars browning too quickly on top, cover the dish with a piece of foil.

Cool & serve – Let bars cool completely in the pan before lifting them out and slicing into squares.