Preheat the oven to 350°F (176°C) and spray muffin pans with nonstick cooking spray. (Use a paper towel to evenly distribute the spray and wipe off excess grease.) This recipe yields about 14 muffins.
In a medium bowl, whisk together the flour, baking soda, salt and cinnamon.
In a large bowl, whisk together the mashed bananas (make sure to use VERY ripe bananas), oil, honey, eggs, buttermilk and vanilla. Fold in the flour mixture until just combined, and stir in the oats and chocolate chips (or nuts).
Fill each muffin cup 3/4 full. Bake for 16 to 18 minutes, or until the tops are lightly browned and a toothpick comes out clean (or with a few crumbs). Leave the muffins in the pans for 5 minutes before removing to a wire rack to cool completely.
Store in an airtight container. These muffins also freeze well. Enjoy!