Carefully heat all ingredients, except for the starch, while stirring. Mix the starch with a little water or milk, add to the liquid and briefly bring to the boil. Fill into cups.
Since the chocolate is very rich, I like to fill it into smaller cups - the amount is enough for 8 people.
Not original, but good: grind some chilli from the grinder over it or use powder.
If you don`t like it so sweet, you can reduce the sugar.