Preheat oven to 350° F. Line an 8 inch x 8 inch baking pan with parchment paper or grease the pan with non-stick spray or butter. Lightly grease the top of the parchment paper.
In small bowl, whisk together the flour, baking soda and salt. Set aside.
In a blender, puree the bananas, sour cream, eggs, oil, vinegar and vanilla until smooth.
In the bowl of an electric mixer (or in a bowl with a hand mixer), cream the butter and sugars.
Add ⅓ of the liquid mixture to the butter/sugar mixer, beating until combined. Add ⅓ of the flour mixture and then ⅓ of the liquid mixture before the flour is fully aborbed. Repeat, ending with the flour mixture, mixing just until the flour mixture is fully absorbed. Be careful not to overmix.
Mix in the chocolate chips, being careful not to over-mix
Pour the batter into the prepared pan and bake 35-40 minutes. A toothpick should come out clean.