Preheat the oven to 325°F.
Beat the butter with the granulated sugar and brown sugar until well incorporated.
Add the egg and vanilla, beating until combined and scraping down the bowl as needed.
Mix in the peanut butter until fully incorporated.
Add the all-purpose flour, whole wheat flour, cocoa powder, flax seeds, baking soda, and salt, mixing until just combined.
Fold in the chocolate chips and banana chips, mixing until evenly distributed.
Scoop the dough onto a baking sheet using a cookie scoop.
Bake for 10 minutes, until just set.