In a small sauté pan, heat on medium and give walnuts a quick toast, for 2-3 minutes turning often to prevent burning. Optional: You could also just add raw walnuts. Pre-heat oven to 350 degrees and lightly grease with some butter (I usually use a butter wrapper or cooking spray).
Sift flour, baking soda, and salt into a medium sized bowl. In another bowl, whisk the eggs and vanilla together.
In a large bowl, cream the butter and sugar either using a stand mixer with the paddle attachment or a hand mixer. After the butter and sugar is creamed but while the butter and sugar is being mixed and light and fluffy, gently pour the egg and vanilla mixture into the butter mixture. Mix until well incorporated.
Add the mashed bananas (the mixture will appear to be curdled, but don't worry!).
With a rubber spatula, gently mix in the flour mixture to the creamed butter and sugar and with eggs. Fold in the toasted walnuts and then pour the batter into the greased loaf pan.
Bake for 50 minutes. Check with a cake tester, toothpick, or a knife for doneness. If it doesn't come clean, bake for another 5 minutes until it does.
Turn to banana bread out of the pan and let it cool on a wire rack.
Serve warm with fresh butter or once cooled, wrap with plastic wrap and store on countertop for 1 -2 days, in fridge for up to a week, or freeze for up to 3 months.