Like chocolate chip cookies, banana bread has adherents of several schools of thought. On one hand, there are those that believe that a good banana bread should be more like a bread: dense, slightly chewy and not very sweet. On the other end of the spectrum there are those that like a sweet, moist, cake-like
Put the oven rack in the middle position and preheat to 350 degrees F. Butter and sugar a 9" loaf pan.
Whisk the flour, sugar, baking soda, baking powder, salt and chocolate chips together in large bowl
In a medium bowl, melt the butter and allow it to cool a little. Measure out the buttermilk and vanilla into a small bowl. Add the egg yolks to the melted butter and the egg whites to the buttermilk. Whisk each seperately until smooth and creamy. Add the buttermilk mixture to the butter mixture and whisk to combine.
Mash the bananas with the back of a fork with the juice of half a lemon. Add this to the liquids and stir to combine.
Dump the liquids into the dry ingredients then gently fold it all together until most of the big lumps of flour are gone. You don't want to over-mix it and it's okay if there are some small bits of flour left. Put it in your loaf pan and gently even off the top.
Put it in the oven until a skewer inserted into the middle comes out clean, about 50 minutes to 1 hour. Allow it to cool on a rack in the pan.