Preheat the oven to 350 degrees Fahrenheit. In a medium sized mixing bowl, mix the all-purpose flour, baking soda, baking powder, sugar, and cinnamon together until all ingredients are evenly distributed. Set the dry mixture aside.
In the bowl of a stand mixer (or a separate mixing bowl), mash the bananas with a fork until there are very few clumps left. (A few clumps is ok). Add the egg, vanilla extract, sour cream, and milk and mix on medium speed in a stand mixer (or with a hand mixer) until all ingredients are combined.
Add the dry ingredients to the stand mixer and mix until all ingredients are just combined. Be careful not to overmix. Gently fold in the mini chocolate chips with a spatula until evenly dispersed.
Line the inside of a 9 x 5 inch baking pan with a baking spray. Pour the batter into the greased baking pan. Place the pan in the oven and bake at 350 degrees Fahrenheit for 55 minutes to 1 hour. You will know that the banana bread is finished when you can poke a butter knife or toothpick into the center and it comes out clean. Let the banana bread cool completely before slicing.