Giant Super Fluffy Pancakes

Name: Giant Super Fluffy Pancakes
Ingredients: Nonstick cooking spray, for the skillets; 3 cups cake flour (see Cook's Note); 6 tablespoons confectioners' sugar; 4 teaspoons baking powder; 1 teaspoon kosher salt; 2 1/4 cups milk; 1 stick (8 tablespoons) unsalted butter, melted and cooled, plus more for serving; 1 teaspoon pure vanilla extract; 2 large eggs, separated, plus 4 whites; 1/2 teaspoon cream of tartar; Maple syrup, for serving; Whipped cream, for serving; Assorted fresh berries, for serving