Preheat your preheated oven to 350°F. Line a muffin pan with muffin liners or lightly grease a prepared muffin tin.
In a large bowl, mash the overripe bananas with a fork or potato masher until smooth. A few small lumps are fine.
3 Large Bananas
Add the melted butter, sour cream, eggs, vanilla extract, brown sugar, and granulated sugar. Beat with a whisk or electric mixer at a medium speed just until combined. Avoid overmixing. Too much mixing causes tough muffins.
½ Cup Brown Sugar, ¼ Cup Granulated Sugar, ½ Cup Butter, ½ Cup Sour Cream, 2 Large Eggs, 1 Teaspoon Vanilla Extract
Add the dry ingredients: flour, baking soda, and salt and stir together a bit before incorporating into the wet ingredients.
1 ½ Cups All-Purpose Flour, 1 Teaspoon Baking Soda, ½ Teaspoon Salt
Gently fold the dry ingredients into the wet ingredients using a rubber spatula until you see only a few streaks of flour remaining. The batter should be slightly lumpy and somewhat thick. This is normal for wet batter.
Fold in the cup nuts, plus chocolate chips if you want a banana chocolate chip muffins variation.
¾ Cup Walnuts, ½ Cup Chocolate Chips
Spoon batter into muffin cups. Divide the batter evenly among the paper muffin cups. Fill each about ¾ full for tall bakery-style muffins.
Bake 18–22 minutes, or until the top of the muffin springs back when lightly touched and a toothpick inserted into the center of a muffin comes out clean.
Let the individual muffins cool in the tin for a couple of minutes, then transfer to a wire rack to cool completely.