Soft and Chewy Banana Bread Chocolate Chip Cookies

0 In a large bowl, add the softened butter, brown sugar, and granulated sugar. 
1 Using a hand mixer or a whisk, mix until the mixture looks smooth and creamy. This should take about 1–2 minutes. Make sure the butter is soft to the touch, not melted, so it blends properly.
2 Add the egg, egg yolk, vanilla extract, and mashed banana to the bowl. Mix again until everything is fully combined and smooth. The mixture may look slightly loose or creamy, which is normal.
3 In a separate bowl, whisk together the flour, cornstarch, baking soda, salt, and cinnamon until evenly combined. This helps make sure the cookies bake evenly.
4 Add the dry ingredients to the wet ingredients and gently mix until just combined. Stop mixing as soon as you no longer see dry flour. Overmixing can make the cookies dense instead of soft.
5 Add the chocolate chips and fold them into the dough until evenly distributed.
6 Cover the bowl and place the dough in the refrigerator for 30 to 45 minutes. This step helps control how much the cookies spread while baking. Do not skip it, but also don’t leave it in too long, or the cookies may bake thicker than intended.
7 Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper so the cookies don’t stick.
8 Once chilled, scoop about 3 tablespoons of dough per cookie and place them on the prepared baking sheets, leaving 1.5-2 inch spaces between each one so they can spread.
9 Bake for 11 to 13 minutes, until the edges look set, but the centers still look slightly soft. This is important for a soft texture, so avoid overbaking.
10 Remove the cookies from the oven and let them cool on the baking sheet for about 5 minutes. Then transfer them to a wire rack to cool completely.