Preheat oven to 400° F and line three baking sheets with parchment paper.
Slice the cold unsalted butter into ¼ inch cubes and place in the standing mixer, along with the brown sugar and cane sugar. Gradually increase speed and mix on high for 3-4 minutes until there aren't any chunks of butter left.
¾ cup cold unsalted butter, 1 ¼ cup light brown sugar, ½ cup cane sugar
While the butter and sugars are mixing, whisk together the all purpose flour, sea salt, cornstarch, baking soda, baking powder, and ground cinnamon in a separate bowl. Set aside.
3 cup all purpose flour, 1 teaspoon fine sea salt, 2 teaspoon cornstarch, ½ teaspoon baking soda, 1 teaspoon baking powder, ¾ teaspoon ground cinnamon
Add the mashed banana, egg, and vanilla extract to the standing mixer and mix on medium speed until creamy and smooth. Scrape down the sides of the bowl halfway through to get an even mix.
¾ cup overripe mashed banana*, 1 large eggs, 2 teaspoon vanilla extract
Add the mixed dry ingredients to the standing mixer and mix on the lowest setting until just barely combined. Add the semi-sweet chocolate chips and chopped pecans while flour is still mixing in--this minimizes the risk of overworking the cookie dough.
2 cup semi-sweet chocolate chips**, 1 ½ cup chopped pecans
Cover the bowl of dough and place it in the freezer for 15 minutes to chill.***
Take the dough out of the freezer and roll it out into 15 individual balls.
Place 5 balls of dough on each baking sheet. Press a few additional chocolate chips and chopped pecans into the top of each. You can also sprinkle some of the leftover pecan crumbs onto the top of each ball of dough.
Bake each baking sheet separately for about 11-13 minutes on the middle oven rack, or until the cookies are starting to brown on the top.
After taking the cookies out of the oven, you can use a round cookie cutter or the back edge of a spoon to round out the edges. Let the cookies cool on the pan for about 15 minutes before digging in. Enjoy!