Turn on the oven. Separate the whites and yolks and whip the whites in a grease-free bowl until curdled in appearance.

Add sugar to the whites 1 tbsp at a time and whip into a dense meringue. Fold in the yolks in parts, continuing to whip.

Turn off the mixer, sift the flour and cocoa into the bowl, fold in quickly and gently with a spatula and pour the batter into the pan.

Bake the sponge for 30-35 minutes at 160°C, until a skewer comes out dry. Let the finished sponge cool, or preferably leave it overnight so it matures.

Make the frosting from strained sour cream, adding the cocoa at the powdered sugar stage.

Cut the sponge into two layers and soak them well with sweet coffee. Place the first layer in a ring, spread most of the frosting on it, cover with the second soaked layer and coat the top with the remaining frosting.

Refrigerate the cake for a couple of hours, then carefully remove it from the ring and decorate with chocolate shavings and cookies.