In a small bowl, take some of the walnuts and brown sugar and set aside.
In your KitchenAid, combine the butter, remaining sugar and eggs until well blended. Add the sourdough starter, vanilla extract, raw honey, olive oil and bananas and blend well.
Slowly add in the dry ingredients (flour, salt, and baking soda) and mix just until combined. Fold in the walnuts.
Pour batter into a greased 9x5 baking dish. Sprinkle the top with the reserved sugar and walnut mixture.
Bake this bread for 55-60 minutes or until a toothpick in the center comes out clean. Allow to cool in the pan for 30 minutes.
Remove from the pan an allow to cool completely.
Wrap leftover bread tightly and refrigerate. Or keep in a ziploc bag.