Melt the chocolate on a steam bath.
Mix the butter with the foam, add the sugar and continue mixing for a few minutes. Add the slightly cooled chocolate and mix until smooth. Then add the yolks one by one, mixing after each one.
Whisk the egg whites separately with a pinch of salt.
Add to the above composition the flour mixed with cocoa, then carefully incorporate the egg whites.
Wallpaper a small round shape with baking paper on the bottom and grease the shape with butter (I used a 17 cm shape but it's ok and a 20 cm one. If you make a bigger shape, double the quantities).
Pour the composition into the mold and put in the preheated oven at 140 degrees for 50 minutes.
Remove from the oven and leave to cool. After it has cooled, cut the top into a thin layer to have a straight cake and because the top is slightly crispy. Then cut the cake in half.
Heat the jam and grease the first countertop with half the amount. Place the second sheet and grease it with the rest of the jam.
Icing: in a bowl put water and sugar on the fire and let it boil for 3-4 minutes. Remove from the heat and add the chopped chocolate, stirring until the chocolate melts. Then pour the icing on the cake starting from the middle and with a knife level quickly. Grease the edges with glaze.
Let cool for at least 2 hours or until the next day.
Serve with whipped cream.