Preheat the oven to 204 degrees celsius. Lightly grease a 12-cup standard muffin tin or line with paper liners. If using liners, lightly grease them as well. Set it aside.
Place all the ingredients except the mix-ins in a blender or the bowl of a food processor fitted with the steel blade: oats, bananas, eggs, greek yogurt, honey, baking powder, baking soda, vanilla extract, and salt.
Blend or process on high, stopping to scrape down and stir the ingredients once or twice as needed, until the batter is smooth and the oats have broken down almost completely, about 3 minutes.
If the batter is warm from the appliance's motor, let the batter cool for 10 minutes.
Divide the batter between the prepared muffin cups, filling each no more than 3/4 of the way to the top. Sprinkle with chocolate chips or nuts as desired (optional).
Bake for 15 minutes, until the tops of the muffins set and a toothpick inserted in the center comes out clean. Place the pan on a wire rack and let the muffins cool in the pan for 10 minutes.
Remove from the pan and enjoy!