In a large bowl, combine flour, brown sugar, white sugar, baking powder and salt.
In a blender, puree spinach, banana, milk, vegetable oil, Greek yogurt, and vanilla extract. Whisk into flour mixture with beaten egg yolks until smooth.
In a bowl, beat egg whites until soft peaks form.
Fold the egg whites into the batter.
Preheat waffle iron. Coat with non-stick spray.
Pour batter onto the hot iron. Cook until golden brown.
Recipe by Sugar, Spice and Family Life at https://sugarspiceandfamilylife.com/2017/03/green-smoothie-waffles-recipe.html