Preheat oven to 350 degrees. Spray with nonstick oil and line a 9 x 12 inch rectangular cake pan with parchment paper.
Using a stand mixer or handheld beaters, cream the butter on high speed in a large bowl for a minute or so.
Add sugar and beat until light and fluffy.
On low speed, scraping down sides of bowl with spatula, add egg, peeled bananas and pure vanilla extract until incorporated.
In a large bowl, sift together the flour, salt and baking powder.
On low speed, alternate adding the flour mixture and the milk until all ingredients are incorporated (do not overmix)
Fold in chocolate chips (or throw em into the mixer if feeling lazy!)
Bake in oven on middle rack for 25-30 minutes, depending on how hot your oven gets. Turn pan halfway through. Check cake after 20 minutes and every few minutes thereafter. (I hate an overdone cake!) Cake is finished when a clean toothpick inserted in middle come out clean.