Preheat oven to 350 degrees and grease a 9x5 inch loaf pan (or mini pans).
In a large bowl, combine the melted butter and sugar.
Add in the eggs and vanilla extract, mixing well.
Add in the flour, baking soda, and salt, stirring until smooth.
Fold in the sour cream, walnuts, and bananas.
Spread mixture evenly into prepared pan.
Place in preheated oven and bake for about 60 minutes, or until toothpick comes out clean when inserted in center.
Remove pan from oven and allow to cool slightly before slicing and enjoying!