Mix the butter with the sugar and vanilla sugar into a paste. Add the egg whites two by two, mixing thoroughly each time. If the eggs were just taken out of the refrigerator, it is necessary to wait for the whites to reach room temperature. Then add the cream, then the sifted flour. Work with a sauce whisk until completely smooth. Use a pastry bag to lay small heaps, 3/4 inch in diameter, on the lightly greased baking sheet. Bake in an oven which was preheated to the maximum (500F). As soon as a brown ring appears, take out of the oven. Still very hot, take the cakes one by one, wrap them immediately around a pencil. They will keep for at least a month in a well closed tin box.
