Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper.
Mash bananas in a large bowl until mostly smooth.
Stir in peanut butter, brown sugar, granulated sugar, egg, and vanilla until combined.
Whisk flour, baking soda, and salt in a separate bowl. Fold into wet mixture until just combined.
Fold in chocolate chips if using.
Scoop rounded tablespoons of dough onto sheets, 2 inches apart. Press down slightly.
Bake 10–12 minutes until edges are golden and centers look barely set.
Cool on sheet 5 minutes, then transfer to wire rack.
These peanut butter banana cookies are soft, naturally sweet, and made in one bowl. Perfect for quick snacks, baby showers, or guilt-free treats.