Start to melt the chocolate for the meringue while the cake is in the oven.
When the 30 minutes are done, take the cake out and start beating the egg whites in a superclean bowl. Continue until they are stiff and you have big peaks. Slowly add the sugar and a little bit of vinegar and beat the egg whites again for a couple of minutes.
Add some cornstarch and cacao and fold it through the egg whites.
Bit by bit, super slowly drizzle the melted chocolate and fold it through. When you’re done, the meringue mixture is ready. Increase the oven temperature to 180. Pour the meringue on top of the cake and bake it in 25 minutes.
Let it cool of slowly, first in the oven with the door open and after half an hour set it on the counter top. The meringue might collaps a little bit, but don’t worry, it still tastes still amazing!