Dissolve yeast in lukewarm milk and cover and rest for 20 minutes or until bubbles appear.
Separate the eggs, adding the egg yolks to the yeasted milk, along with the melted butter, vanilla extract, and dry ingredients (flour, salt, sugar). Set egg whites aside.
Mix well using a rubber spatula, then cover the bowl and let the batter rest in a warm place until the dough has doubled in size (roughly one hour, or up to overnight in the refrigerator covered in plastic wrap).
Preheat your belgian waffle maker.
Beat the egg whites until frothy, then add the beaten egg whites and sparkling water to the yeast dough to make it runny.
Spray the preheated waffle iron with nonstick cooking spray, then pour 1 cup batter into the hot waffle iron and cook the Belgian waffle batter until your waffle is golden brown and crispy.
For best results, eat immediately dusted with powdered sugar!
If you are making waffles for a crowd, put your homemade waffles on a baking sheet in an oven preheated to 200 F to keep warm.