Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a large bowl, mash the bananas until mostly smooth. Stir in the Greek yogurt until well combined.
Add honey or maple syrup and the egg if using; mix until even.
In a separate bowl, whisk together the rolled oats, baking powder, baking soda, cinnamon, and salt.
Pour the dry ingredients into the wet mixture and stir just until combined — don’t overmix.
Fold in your chosen add-ins (nuts or chocolate chips work great).
Divide the batter evenly among the muffin cups.
Baking
Bake for 20–25 minutes, until the tops are set and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Let muffins cool in the tin for 5–10 minutes, then transfer to a wire rack to cool completely.
Store leftovers in an airtight container.
Notes
For a lower-sugar version, omit the honey/maple syrup. If needed, pulse the oats in a food processor for a finer crumb. Avoid overmixing to prevent gumminess.