Cornbread with Honey Butter

Name: Cornbread with Honey Butter
Ingredients: 1 cup whole milk; 1/3 cup unsalted butter, melted; 1 large egg, separated; 1 cup medium-grind cornmeal; 1 cup all-purpose flour; 1/3 cup granulated sugar; 3 tablespoons plus 1 1/2 teaspoons baking powder; 1 tablespoon kosher salt; 1 teaspoon cornstarch; Nonstick cooking spray, for pan (I like duck fat cooking spray); 1 stick (8 tablespoons) unsalted butter, softened; 1/4 cup honey; 1/2 teaspoon pure vanilla extract; 1/4 teaspoon ground cinnamon or smoked cinnamon; Small pinch kosher salt