Place the gelatine sheets in a bowl of cold water and allow to soften.
Mix the egg yolks and sugar in a bowl, until they are pale and creamy.
Heat the milk in a saucepan and bring it to a boil, then pour it over the egg yolk mixture and whisk until combined.
Return the mixture to the pan and cook until thickened and a thermometer reads 82C.
Remove from heat and stir in the bloomed gelatine then strain it over the melted Dulcey chocolate.
Mix until smooth and creamy then cool to room temperature and fold in the whipped cream.
Take a 6 cavity semi-sphere mould and fill about a 1/3rd with Dulcey mousse, using a small palette knife spread the mousse up the sides of the mould ensuring none of the mould can be seen.
Take the frozen hazelnut mousse semi-spheres and place them in the mould, seal them up with more valrhona dulcey mousse on top and smooth the tops. Place in the freezer and allow to set.