Add the milk, egg yolks, vanilla and 1 tbsp of of caster sugar into a bowl. Beat with a large whisk until thick, smooth and creamy. Sift the flour and baking powder, then fold into the yolk mixture.
In a separate bowl, whisk the egg whites until they turn pale white. Slowly, add 2 tbsp. of caster sugar, whisking as you go. Continue to whisk until the egg whites are glossy and hold a stiff peak shape when you remove the whisk.
Put your frying pan, on the lowest heat possible. Lightly coat the pan and rings in a little oil and leave to heat up while you continue making your mixture.
Using a metal spoon, lightly fold the whisked egg whites into the yolk mixture, folding gently ensuring you keep a light, fluffy texture. Gently pile 3 tablespoons of mixture into the pan. Leave to cook for 5 to 6 minutes until the pancakes have risen and firmed enough to be able to carefully flip over. Flip them over and cook for a further 3 to 4 minutes.