Preheat your oven to 450°F, positioning the rack in the middle.
In a blender, blend together the flour, milk, eggs, egg whites, remaining 2 tablespoons of NOOC Wild Mushroom & Sage Olive Oil, sugar, salt, and freshly ground pepper until smooth.
Pour the batter over the caramelized onions in the skillet.
Sprinkle the top with grated cheddar cheese (or your preferred cheese) and add crispy bacon or ham if desired.
Bake in the preheated oven until the pancake is puffed and golden, about 15 minutes.
Serve immediately with a drizzle of NOOC Denissimo Balsamic Vinegar. Note that the pancake will deflate quickly, which is normal.