Whisk 1 3/4 cups flour, 1 tablespoonsugar, 2 teaspoons baking powder,1 teaspoon baking soda, and 1 teaspoonkosher salt in a large bowl.Using an electric mixer, beat3 large egg whites in a mediumbowl until medium-softpeaks form.
Whisk 3 large eggyolks, 1 cup (2 sticks) meltedbutter, 1 cup buttermilk, and3/4 cup soda water in a mediumbowl; gradually whisk into dryingredients. Fold in egg whites.Coat waffle iron with nonstickvegetable oil spray.
Pourbatter onto iron, spreading itinto corners (amount of batterneeded will vary according tomachine). Scatter 1 roundedtablespoon thin strips of ham and1 tablespoon shredded sharp whitecheddar over each waffle. Cookuntil golden brown and cookedthrough.
Transfer to a bakingsheet; keep waffles warm inoven between batches.