This is a rich and flavorful banana bread with complex toffee nuttiness thanks to the browned butter and blend of white whole wheat and all-purpose flour. You can use all whole-wheat flour, but the bread will be denser. The walnuts aren’t really optional, they perfume the bread while it bakes and complement the butter and wheat flour.
I really hope you make this for yourself or someone you care about. After making hundreds of “best banana bread” recipes, this is the one I’ve arrived at.