Preheat oven to 350°F. Line a cookie sheet with parchment paper. Set aside.
In a small bowl, add the 2 bananas. Use a fork to mash them and set them aside. To prevent the bananas from turning brown, add a little lemon juice.
To a medium mixing bowl, add the flour, baking soda, salt, and cornstarch. Whisk to combine. Set aside.
To a large mixing bowl, add the butter, brown sugar, and granulated sugar. Use a hand mixer to beat on medium speed until light and fluffy.
Add in the mashed bananas and vanilla extract. Beat on medium just until the bananas are worked in.
Pour in the dry ingredients and mix with the hand mixer until incorporated. (The dough will be very thick.)
Set aside ¼ cup of milk chocolate chips.
Use a spatula to fold in the remaining chocolate chips.
Using a 1½ tablespoon cookie scoop, scoop the cookies onto the lined cookie sheet, spacing them 2 inches apart.
Add 3-5 chocolate chips from the reserved ¼ cup to the tops of each ball of cookie dough.
Place into the oven and bake for 9 minutes. Turn the cookie sheet and bake for an additional 2 minutes - a total of 11 minutes. (You may not need to turn should you have a convection oven.)
Let the cookies cool on the cookie sheet for 5 minutes before transferring them to a cooling rack or a paper towel-lined counter.