Preheat the oven to 200°C.
Crush the gianduja.
Beat together the eggs and the sugar (a cold sabayon) until the mixture is light and fluffy. Place the butter and chocolate in a bowl and melt over a bain marie.
Add the chocolate and the flour to the sabayon a little at a time.
Line the metal rings with baking parchment. Pour the chocolate mixture into the moulds until 3/4 full and then sprinkle with the crushed gianduja.
Transfer to the oven and bake for 6 to 7 minutes.
Place the milk and the pistachio paste in a pan and bring to the boil. Beat together the egg yolks and the sugar until the mixture is pale and fluffy.
Add the milk to the egg and then return to the pan. Heat to 84°C, stirring constantly until the mixture coats the back of a spoon.
Serve with the chocolate fondant.
«If you do not have pistachio paste, feel free to use pistachio flavouring.»