1. Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.
2. In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
3. In a large bowl, cream together the softened butter and sugar until light and fluffy, about 3-4 minutes.
4. Beat in the eggs one at a time, followed by the vanilla extract. Mix in the mashed bananas until well combined.
5. Alternately add the flour mixture and the sour cream to the banana mixture, starting and ending with the flour. Stir just until combined.
6. Fold in the chopped walnuts, if using.
7. Pour the batter into the prepared pan, spreading it evenly.
8. Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center of the cake comes out clean.
9. Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.

One of my favorite memories is baking with my siblings, each of us taking turns to mix or pour. It was chaotic but filled with laughter and love. Remember, the key is to not over-mix the batter; it should be just combined to ensure a tender crumb.