We like these since they resemble regular waffles and that's always a good thing.
Sift the flour, baking soda, baking powder, and salt.
Mix the egg yolks with the sour cream. Add the buttermilk, then the milk, then the butter. Add the vanilla. Whisk well.
Pour the wet onto the dry and fold to incorporate. Allow to stand for 10 minutes.
Whisk the whites in a clean bowl. When soft peaks start, add the sugar and whisk to stiff peaks.
Fold the egg whites into the base in quarters.
For my waffle iron, a size 8 scoop was too big. The batter was not different in how it cooked from other batters, so what you normally do should suffice.
I used Namaste brand gluten-free flour. This flour has Xanthan gum added.