Preheat your oven to 325 degrees (for a glass pan) or 350 degrees (for a metal pan)
Grease an 8x11 pan and set aside
Combine milk and white vinegar in a bowl and let sit. This will create soured milk. Buttermilk may be used in place of the soured milk and the vinegar can be omitted.
In a medium bowl, whisk together the flour, baking soda, and salt.
In the bowl of a stand mixer (or in a large bowl with a hand mixer), cream together the sugar and softened butter. Beat on high for 3 minutes, scraping down the sides 1-2 times.
Add the eggs and mix until fully combined.
Add the vanilla and mashed bananas. Mix until just combined.
Add 1/3 of the dry ingredients and mix a few times. Next, add 1/2 of the soured milk (or buttermilk). Then mix in another 1/3 of the dry mixture followed by the soured milk. Finish with the last of the dry mixture and stir until just combined (a few dry streaks is okay).
Fold in the chocolate chips.
Spread the banana chocolate chip cake into the greased cake pan.
Bake for 55 minutes, until a toothpick inserted in the center of the cake, comes out clean.