Preheat the oven to 375°F/ 190°C. Line a 12-cup muffin tin with liners.
In a bowl, combine the flour, baking soda and salt. Set aside.
In another bowl, use a fork to smash those bananas. Mix in the brown sugar and whisk till the sugar melts into the banana. If making this overnight, just stir in. The sugar will melt overnight.
Stir in the cooled, melted butter. Whisk in the eggs, vanilla extract and nuts. Reserve some nuts to sprinkle on top.
Fold in the dry ingredients. Spoon into the prepared muffin tins.
Bake at 375°F/ 190°C for 20 minutes, or until a skewer inserted into the center comes out clean.
Cool on a wire rack before serving.