Start the oven at 180 degrees Celsius.
Process the graham biscuits to crumbles in a blender.
Melt the margarine and mix it together with the crumbles.
Place the mixture in a baking form an cover the bottom and the edges with the crumbles.
Put the form in the middle of the oven for 10 minutes. Take out the form and let it rest so the cake bottom becomes cold.
With an electrical mixer make a hard foam of the heavy cream. Add the cream cheese and make it all soft.
Pour half of the Nutella in the mixture and stir it all together to a hard foam.
Place evenly the other half of the Nutella on the cake bottom, and then the mousse on top of it.
Put the cake in the fridge until it is time to serve.