Preheat waffle iron. Preheat oven to 200 degrees F.Advertisement
Sift flour, cocoa, baking powder, baking soda and salt into a mixing bowl.
Whisk egg yolk, buttermilk, brown sugar, oil, vanilla and coffee granules in a medium bowl. Whisk into dry ingredients until just moistened.
Beat egg whites in a clean mixing bowl with an electric mixer until soft peaks form. Gradually add sugar, beating until glossy but not dry. Whisk one-quarter of the beaten whites into the batter, then fold in remaining whites.
Lightly coat waffle iron with cooking spray. Spoon in the batter and cook until the waffle is crisp and golden. Transfer to oven to keep warm. Repeat with the remaining batter, lightly coating iron with nonstick spray each time, if necessary. Dust the waffles with confectioners' sugar before serving, if desired.
Make Ahead Tip: Refrigerate leftover waffles for up to 2 days or freeze for up to 3 months. Reheat in the toaster.
2 1/2 other carbohydrate, 1 fat