INGREDIENTS 2 1/4 cups all-purpose flour1 teaspoon baking soda1/2 teaspoon salt1 stick unsalted butter, softened, plus 2 tablespoons, melted and cooled1 cup sugar, divided2 large eggs1 1/4 cups mashed very ripe bananas (about 3 medium)2/3 cup plain whole-milk yogurt1 teaspoon pure vanilla extract1 (3 1/2- to 4-ounce) bar 70%-cacao bittersweet chocolate, coarsely chopped1 cup walnuts…