Preheat the oven at 180 degrees Celsius.
Cover a baking form 20 x 30 cm.
Melt the margarine in a casserole, and then mix it with the sugar and vanilla sugar.
Add the eggs, flour, salt and the cacao powder and mix everything together.
Pour the batter in the baking form and place in the middle of the oven for 15-20 minutes. Take out the cake and let it cool down.
Melt the margarine and the chocolate in a casserole, and then add the nutella and stir it all together well.
Pour it evenly on the cake and put it in the fridge for 1 hour.
Melt the chocolate and the margarine in a casserole and mix well. Spread it evenly on top of the fudge.
Place the brownie cold for minimum 30 minutes before cutting it in small squares and serving it.