Preheat your oven to 350 degrees and line a rimmed baking sheet with parchment paper.
In a large bowl whisk together flour, baking soda and salt. Set aside.
In a large bowl with a hand mixer or in the bowl of a stand mixer fit with the paddle attachement, beat together the butter, granulated sugar, and brown sugar. Beat until the sugar is light and fluffy about 3 to 6 minutes.
Add in the mashed banana until fully combined. Then beat in the egg yolk. Finally beat in the vanilla extract.
Add the flour mixture all at once. Beat on low until combined enough that you can turn the mixer on high. Stop mixing when just combined. Be careful not to over mix.
Stir in the chocolate chips. Using a 1 1/2 tablespoon cookie scoop, scoop the cookies into balls and drop them on the prepared baking sheets. Bake for 10 to 12 minutes, rotating the pan once during baking.
Remove from the oven. Allow to cool on the pans for 2 minutes before transfering to cooling racks to cool completely. Once cooled, store in an airtight container for up to 1 week.