Begin by preheating the oven to 425 degrees. Lightly spray a muffin tin with non-stick spray.
Melt ¼ cup of unsalted butter and set aside to cool.
Using a large whisk, mash 4 ripe bananas.
Add the coconut sugar, cooled butter, eggs, Greek yogurt, vanilla extract and whisk well. Regular low-fat yogurt can be substituted in place of the Greek yogurt.
In a separate bowl whisk together the flours, baking powder, and salt.
Slowly add the dry ingredient to the wet ingredients and whisk until fully combined.
Add the Old-Fashioned Oats and using a rubber spatula, mix until combined.
Divide the batter evenly in the prepared muffin tin and top with oats.
Bake for 5 minutes at 425 degrees then lower the oven to 375 and bake for an additional 25 minutes.