How to make
Separate the yolks from the whites and beat the egg yolks with sugar. Beat the whites into thick snow and carefully mix the egg yolks in. Mix with the flour and vanilla until homogeneous. Put the mixture into a square oven dish, covered with a slightly greased baking sheet.
Even out the layer well and put it to bake in a preheated oven. Turn the hot layer upside down on a towel and carefully remove the paper. Using a towel, roll up the layer and leave it for at least 10 minutes. Then unroll it and smear it with the prepared cream. Roll it up once more and put it in the fridge for a few hours.
To prepare the cream mixture, beat the eggs and add sugar, flour and sour cream. Put the mixture to thicken in a water bath, while stirring. Leave it to cool.
Beat the butter very well, add it to the cream and blend everything with a mixer. The cream must not be hot when you smear the roll.
