How to cook
Beat the eggs with the sugar until whitened. Gradually and carefully add the sifted flour to them, while stirring with a wooden spoon.
Add the vanilla. Pour the mixture into a rectangular oven dish, covered with baking paper.
Bake in a preheated oven until ready.
Make the buttercream by beating the butter with the powdered sugar and cocoa with a mixer.
Smear the baked and cooled cake layer with the buttercream and then with the strawberry jam. Sprinkle with crumbled walnuts and roll it up.
Sprinkle the ready roll with powdered sugar mixed with cocoa.