Begin by whisking together the flour, baking soda, cornstarch, and salt in a medium-sized bowl. Set this dry mixture aside for later.
In a separate bowl, cream the softened butter, mashed bananas, brown sugar, and granulated sugar until they are well combined and creamy.
Add the vanilla extract to the banana mixture and continue mixing until it's fully incorporated.
Gradually fold the dry flour mixture into the wet ingredients, careful not to overmix. Stir just until everything is combined.
It's time to add the star ingredients! Gently stir the chocolate and peanut butter chips until they are evenly distributed throughout the dough. Combining sweet chocolate and nutty peanut butter will take these cookies to the next level.
Preheat your oven to 375°F (190°C) and line a cookie sheet with parchment paper to prevent the cookies from sticking.
Use a cookie scoop to drop dollops of cookie dough onto the prepared cookie sheet, spacing them about 2 inches apart. This will allow room for the cookies to spread as they bake.
Bake your cookies for 10 to 12 minutes or until they turn light brown on top. Be careful not to overbake them; you want them to remain soft and chewy.
Once out of the oven, let your cookies cool on a cooling rack. The patience here pays off as it allows the cookies to set and become chewier.
Finally, store your Peanut Butter Banana Chocolate Chip Cookies in an airtight container. They can last up to a week, though we doubt they'll stay around that long—they're just too delicious!