Banana Bread with Walnuts and Flaxseed

Name: Banana Bread with Walnuts and Flaxseed
Ingredients: 2 tablespoons unsalted butter, melted, plus 1 teaspoon unsalted butter, softened, for pan; ½ cup whole-wheat flour; ¾ cup all-purpose flour; ¼ cup ground golden flaxseed (from about 2 tablespoons whole); ¾ teaspoon coarse salt; ½ teaspoon baking powder; ½ teaspoon baking soda; 1 large egg, plus 1 large egg white; ½ cup light-brown sugar; 1 ½ teaspoons pure vanilla extract; ¾ cup mashed very ripe bananas (about 2 medium bananas); ½ cup walnuts (about 1 ¾ ounces), toasted and coarsely chopped