Procedure:
1. Beat the yolks with half the sugar.
2. Add the vanilla essence and melted butter.
3. Add the sifted dry ingredients and mix.
4. Beat the egg whites until stiff with the rest of the sugar and add this mixture to the previous preparation, little by little and with enveloping movements.
5. Cover a 30 x 45 cm side plate with buttered parchment paper and distribute the preparation forming a thin layer.
6. Cook in a preheated oven at medium temperature (180º C) for approximately 10 minutes.
7. Unmold hot on a piece of parchment paper sprinkled with bitter cocoa. Roll up and let cool.
8. For the filling, beat the cream with the powdered sugar and the vanilla essence until whipped.
9. Unroll, fill with the cream and roll. Let cool well.
10. To cover, melt the chocolate with the butter in a bain-marie or in the microwave and cover the roll.