Once the mixture is pale and fluffy, reduce the mixer speed to its lowest setting. Beat in 2 large eggs, one at a time, only adding the next egg until the egg before it has been fully incorporated. Once the eggs have been incorporated, add 1 tablespoon vanilla extract and 1 3/4 cups ripe bananas and continue mixing until just incorporated. Finally, add half the dry ingredients (from the 1st step) until just combined, before adding 1 cup sour cream until just combined, and then the remaining half of the dry ingredients. It's important to mix until just combined — DO NOT OVERMIX, or your cake will be dense and tough and I will cry. It's even better to stop the mixer before the last addition of the dry ingredients is fully incorporated and to continue mixing by hand — 1 or 2 flour streaks left in the batter is totally okay.