Preheat oven to 350 degrees F. Grease an 8x4-inch loaf pan and then line with parchment paper so that it hangs over the two long sides.
In a large bowl, whisk together the flour, baking soda and salt; set aside.
In a separate large bowl, whisk together the banana, peanut butter, sugars, buttermilk, oil, eggs and vanilla extract until smooth.
Pour the wet ingredients into the flour mixture and fold together with a rubber spatula until completely combined and there are no spots with raw flour. Gently stir in the chocolate chips.
Transfer the batter to the prepared loaf pan, smoothing the top into an even layer. Bake until the loaf is golden brown and a toothpick or thin knife inserted into the center comes out with just a few moist crumbs, 1 hour to 1 hour 15 minutes. If your bread appears to be browning too quickly, place a tented piece of foil over it (I did this at the 45-minute mark).
Allow the bread to cool in the pan for about 10 minutes, then turn it out onto a wire rack to cool completely. The cooled bread should be wrapped tightly in plastic wrap; it can be stored at room temperature for up to 5 days.
Nut Butter Substitutes: You can use Sunbutter, almond or cashew butter (make sure it does not have oil separation - I recommend Barney Butter), or Nutella.
Mix-Ins: Use different types of chocolate chips, butterscotch chips, chopped nuts (walnuts, pecans or peanuts work great!), raisins, or even cooked, chopped bacon bits.
Storing: For moist banana bread, keep your loaf wrapped tightly in plastic wrap and then stored in an air-tight container for up to 5 days at room temperature.
Freezing: You can store the whole loaf or slices of this banana bread in the freezer for up to 1 month. Wrap tightly in plastic wrap and then cover with foil. Leave wrapped while thawing.
Converting to Muffins: Fill muffin cups two-thirds full and bake at 375 degrees for 25 to 30 minutes.