Preheat your waffle iron.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
In another bowl, mix the milk, egg yolks, vegetable oil, and vanilla extract.
Combine the wet ingredients with the dry ingredients until just mixed. Do not overmix.
In a clean bowl, beat the egg whites until stiff peaks form.
Fold the beaten egg whites into the batter.
Spoon the batter into the preheated waffle iron and cook until golden brown.
Serve the waffles with fresh blackberries and a dollop of whipped cream.