In a medium bowl whisk together the flour with the baking powder, kosher salt, and brown sugar.
In a small mixing bowl beat the egg whites on medium speed until stiff peaks form, about 45 to 60 seconds.
In a large bowl, beat the egg yolks on medium speed until light and lemon in color, about 1 minute. Whisk in the melted butter.
Whisk the flour and brown sugar mixture into the eggs and butter, adding about ¾ cup at a time alternating with the milk, beginning and ending with the flour.
Stir in the vanilla extract and the toasted pecans.
Gently fold in the beaten egg whites.
Let the batter rest about 10 minutes while you heat up a waffle iron, using a medium heat setting.
Ladle batter into the waffle iron, top with a sprinkling of brown sugar and toasted pecans and bake until the waffles are golden about 3 to 5 minutes. Serve the waffles hot with butter plus warm maple syrup, a bit of brown sugar and more toasted pecans.