Preheat your oven to gas mark 4/180°C/fan 160°C. Butter and line two 10cm cake tins with baking parchment.
Place the dry cake ingredients, egg, milk, vanilla extract and vegetable oil, into a mixing bowl. Beat the mixture until smooth.
Add the boiling water and mix until smooth.
Divide the cake mix between the two cake tins and bake in the oven for 15–25 minutes.
Allow the cakes to cool in their tins.
For the chocolate cream middle, heat the chocolate and cream over a low heat until melted. Away from the heat, whisk the mixture until smooth. Allow to cool.
Remove the cakes from their tins.
Spread the chocolate cream over the top of one of the cakes then carefully sandwich the cakes together.
Melt the remaining chocolate in a pan over water and pour over the top of the cake and allow to cool.
Spread the chocolate hazelnut spread over the top of the cake and decorate the top of the cake with Guylian Sea Shell Chocolates.