Melt chocolate and set aside.
Place egg yolks and milk in a bowl over a pan of simmering water.
Whisk vigorously and the mixture will thicken as air is incorporated and the egg yolks cook. Be careful not to overcook the eggs and set aside once the mixture is thick and glossy.
Cook pumpkin puree, brown sugar, butter, cinnamon and nutmeg, until it becomes like a paste. Add nutella and cook until mixture starts to come together.Fold the pumpkin mixture into whisked eggs and milk.
Fold in melted chocolate into above mixture
Using a stick blender to blend mixture until smooth.
Line rectangular loaf pan with aluminum foil and place a thin layer of shop bought chocolate cake.
Pour mixture on top of the cake.
Line rectangular loaf pan with aluminum foil and place a thin layer of shop bought chocolate cake.
Set mold in fridge overnight. Remove from fridge and de–mold. Cut into portions.