Preheat the oven to 350 degrees F. Line a 12-cup regular-sized muffin tin with paper liners.
Cut two of the bananas into pieces and place in the bowl of a stand mixer fitted with the whisk attachment, or use a hand mixer. Add the brown sugar and whip on medium high speed for around three minutes or until pretty smooth.
Add the melted butter, eggs and vanilla to the banana sugar mixture, and keep whipping for another 2 - 3 minutes, until well combined.
Mash the remaining two bananas in a small bowl until mostly smooth, with only small chunks remaining.
In a medium bowl, whisk together the flour, baking soda and salt. Remove the bowl from the stand mixer and fold in the flour mixture with a rubber spatula until just combined. Fold in the mashed bananas.
Divide the batter evenly in the muffin cups. Sprinkle the tops with pecans and bake for about 18 to 20 minutes until a toothpick inserted in the center comes out clean.
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Notes
Storage: Store in an airtight container at room temperature for up to 3 days. To freeze, place the muffins on a baking sheet lined with a baking mat or parchment and freeze. Transfer to an airtight freezer-safe container or ziplock bag.Adapted from the Food NetworkBanana Nut Muffins