Preheat oven to 350 degrees then spray a 24-count mini muffin pan with nonstick spray and set aside. (No need to spray if using a silicone muffin pan)
Add mashed bananas, maple syrup, butter, egg or flax egg, and vanilla to a large bowl then whisk vigorously until combined (alternatively you could use a stand mixer or hand mixer.) Add flour, baking soda, cinnamon, nutmeg, and salt then whisk until combined. Fold in chopped pecans.
Scoop 2 Tablespoons batter into each mini muffin cup then bake for 10-12 minutes, or until a toothpick inserted into the center comes out clean (err on the side of under-baking vs over-baking.) Cool for 5 minutes in the muffin pan before transferring to cooling rack to cool completely.