Method:

Make the pancake filling: mix the cottage cheese with and 1 egg yolk. Set aside in a cold places.

Make the batter:

Mix the milk and the flour. When the mixture is fluid, incorporate the second egg yolk and sugar.
Whisk the egg whites until stiff and incorporate in the batter; it should be thick but fluid.

Lightly grease a frying pan with oil using a paper towel.
Place a ladle of batter in the frying pan and spread it evenly in a thin layer.
Cook for 3 minutes on each side.

Spread the filling over the pancake and fold it