In a medium bowl, whisk the buttermilk, oil, egg YOLK and vanilla. Pour into the dry mixture and whisk until just mixed. Let sit for 10 minutes.
Using your Kitchen Aid or other electric mixer, beat egg white until stiff peaks form. Fold into batter.
Heat waffle iron. When hot, pour about ¾ cup batter onto hot griddle. (Optional: I sprinkle chopped pecans on batter here) Close and invert. (I love the Presto FlipSide Belgian Waffle Maker) Cook until waffle is brown and crisp, about 4 minutes.
Remove and place waffle directly on wire rack of oven to keep warm while cooking remaining waffles.
Serve with your favorite accompaniments like butter, syrup, fresh fruit or powdered sugar.