Preheat the oven to 350 degrees Fahrenheit.
Spray and line the bottom of an 8x8 baking pan and set aside.
Add the bananas to your blender and puree. Measure out 1 cup worth in a measuring cup. For some reason, even if the banana hits the 1 cup mark on your blender, actually measure out 1 cup in a proper measuring cup, mine never end up the same! Go by what your measuring cup says, not your blender.
Add the pureed banana to a large bowl with all wet ingredients. Beat with an electric mixer.
Add in the dry ingredients, making sure to spoon and level the flour. Beat just until combined.
Transfer to your pan and bake for 28-32 minutes or until a toothpick comes out clean.
Let cool in the pan for about 15 minutes, then flip onto a cooling rack, peel off the parchment paper on the bottom and let cool completely. If you want to speed up the process, stick it in the fridge for about 90 minutes.
To make the frosting, beat together the room temperature butter and cream cheese for about 30 seconds. Beat in the cocoa and powdered sugar until smooth. Beat in the vanilla, salt and milk if needed to thin.
Once the cake has cooled, add the frosting and serve. I sliced mine into 9 slices, but you can easily do 12-16 smaller slices instead.