Preheat and prepare your waffle iron according to the manufacturer’s directions.
In a large bowl, place the flour blend, xanthan gum, sugar, baking powder, baking soda and salt, and whisk to combine well.
In a separate bowl, whip the egg whites with a hand mixer (or in a stand mixer fitted with the whisk attachment) until stiff (but not dry) peaks form.
Place the egg yolks and oil in a separate large bowl and blend with a hand mixer (or in a stand mixer fitted with the paddle attachment) until creamy.
Add the yogurt and milk, and blend until well combined. Add the dry ingredients, and blend again. The mixture will be smooth and thickly pourable.
Fold the beaten egg whites gently into the large bowl of batter until only a few white streaks remain.
Pour or scoop about 3/4 to 1 cup of batter into your prepared waffle iron (more or less depending upon the size and shape of your iron), and spread the batter into an even layer.
Close the lid and cook until steam stop escaping from the waffle iron, between 4 and 5 minutes, depending again upon the capacity of your waffle iron.
Remove the waffle from the iron and serve immediately. Repeat with the remaining batter.
If you do not serve each waffle as soon as it is made, refresh the waffles by placing them in a toaster oven at 400°F for about 3 minutes.
Waffles can also be cooled completely, wrapped tightly and frozen, then defrosted and refreshed similarly before serving.
