Take a big mixing bowl and blend the butter and sugar together by using an electric mixer. Blend at high speed for about 2-3 minutes, until it turns smooth.
Next, incorporate the eggs and vanilla into the mixture by mixing them well until they're thoroughly combined.
Stir in the mashed bananas uniformly into the muffin mix.
With a low-speed whisk, carefully mix the baking soda, cinnamon, and flour until the batter is free of any dry ingredient clumps.
Mix in the chopped walnuts to the muffin mix, ensuring they're spread evenly.
Prepare a muffin tray with liners and evenly distribute the prepared batter into the liners.
Bake the muffins for about 20 minutes or until a toothpick comes out clean when inserted in the middle of the muffins.
Notes
You can keep any leftover muffins in a sealed plastic bag at room temperature for up to 4 days or refrigerated for 5 days.
For best results and maximum flavor, use overripe bananas. Unripe bananas might not mash or blend into the batter as well.
These muffins taste fantastic when garnished with some extra chopped walnuts.
Cinnamon enhances the taste of the walnuts and counterbalances the sweetness of the bananas.
Other nut options for these muffins include pecans and almonds.