Banana Chocolate Chip Cookies

Preheat the oven to 350 degrees F. Line a parchment sheet with parchment paper. In a large bowl, mash up the banana.
Then add brown sugar, sugar, melted butter, egg yolk, and vanilla extract. Use an electric mixer to mix everything together until combined, fluffy and smooth, about 2-3 minutes.
In a separate bowl, mix together all purpose flour, baking soda, cornstarch, cinnamon, nutmeg, and kosher salt. Whisk until everything is mixed together, about 30 seconds.
Add the dry ingredients into the wet ingredients. Fold everything together with a flat spatula or spoon. Mix until just combined and you don't see any streaks of flour, about 1 minute. Then add the semi-sweet chocolate chips and chopped pecans. Continue to fold together until combined.
Place in the refrigerator uncovered for 20 minutes.
Line a baking sheet with parchment paper. Scoop out 1/4 cup of the cookie dough and place onto the prepared baking sheet. Bake about 3-4 cookie dough balls at a time.
Bake for 12-13 minutes, until the edges are set and the centers are puffy.
Fresh out of the oven, Use a small bowl and place it on top of each cookie and swivel in a circle to get a perfectly round cookie, then allow the cookies to chill on the baking sheet for 10 minutes. Then remove entirely and place onto a wire rack.