Best-Ever Banana Bread

Preheat oven to 350º. Line a loaf pan with parchment paper and grease with cooking spray. In a large bowl, whisk together flour, baking soda, and salt. In another large bowl, mix together melted butter, sugar, egg and egg yolk, sour cream, and vanilla. Add mashed bananas and stir until combined. Gradually add dry ingredients to wet ingredients until just combined.  Fold in chocolate chips and walnuts and transfer to prepared loaf pan. Bake until a toothpick comes out clean, about 1 hour. Let cool 10 minutes in pan, then turn out onto a cooling rack to cool completely.