In a pan, mix the egg yolks with the sugar, cornflour and milk in that order.
Add the hazelnuts and put on the heat. Bring just to the boil, stirring constantly, then remove from the heat and leave to cool.
Beat the egg whites to soft peaks and fold into the hazelnut mix.
Place the mousse in the fridge for 2 hours.
When ready to serve, fill individual glasses with the mousse and pour the chocolate and pecan sauce over.
Heat the cream.
When it comes to the boil, add the chocolate and pecans and stir until you get a thick, smooth sauce.