1. Preheat the oven to 350 degrees F. Pop paper liners in the cups of a regular-size 12-muffin tin.
2. Place the flour, baking soda, and salt in a small bowl and whisk to mix. Set the flour mixture aside.
3. Place the butter and sugar in a large mixing bowl and, using an electric mixer, beat them until light and fluffy, about 3 minutes. Add the eggs one at a time, then add the vanilla. Blend in the mashed bananas and buttermilk along with the orange zest or cinnamon, if using.
4. Using a wooden spoon, add the flour mixture to the banana mixture in batches, mixing until each addition is just incorporated. At the end the batter should be barely blended (it will be thick). Fill each muffin cup liner three quarters full of batter. Sprinkle mini chocolate chips evenly over the tops of the muffins, if using.
5. Bake the muffins until they spring back when pressed lightly in the center and a toothpick inserted into the center of a muffin comes out clean, 23 to 27 minutes. Let the muffins sit in the muffin tin on a wire rack for 5 minutes, then gently turn them out of the tin and let them cool upright on a wire rack.