Peel, core and finely slice the apples. Set to one side.

In a large bowl, mix together the egg yolks, flour, milk, salt, sugar and cinnamon until well combined. Stir in the sour cream, if using.

In a separate very clean bowl, whisk the egg whites until stiff. Add the egg whites to the rest of the pancake mixture and fold with a metal spoon. Stir in all the apple slices.

On a medium heat, heat one tablespoon oil in a large frying pan. In batches, spoon some of the batter into the pan to make pancakes the size of American breakfast pancakes. Fry on one side until golden brown (about two minutes) before flipping over to cook on the other side. Transfer to a plate and continue cooking the rest. Add a second tablespoon of oil to the pan half way through. You should have enough for 12 pancakes.

Serve the pancakes whilst hot, dusted with icing sugar and cinnamon.