Preheat the oven at 200 degrees Celsius.
Melt the margarine and the chocolate in a casserole.
Stir the sugar, vanilla sugar and the eggs together, and add the margarine and chocolate in the mixture.
Pour the flour, cacao powder, and the salt in the batter and and mix well.
Place a baking paper in a baking form and pour the batter in the form. Place the cake in the oven for 10 minutes. Let the cake rest a few minutes before serving it.