1. Begin heating up your waffle iron.
2. In a large bowl, combine whole wheat flour, all purpose flour, baking soda, sugar, and salt. Whisk to combine.
3. Create a well in the middle of the flour.
4. In the center of the well, add milk, egg, butter, and vanilla.
5. Mix all ingredients in the bowl together until smooth.
6. In a separate bowl, beat egg whites until stiff.
7. Gently fold egg whites into batter.
8. Spray hot waffle iron with non-stick cooking spray.
9. Gently pour ½-3/4 cup batter into waffle iron.
10. Cook until brown, about 4-5 minutes each, depending on your waffle iron.
11. Serve immediately or freeze and reheat when desired.