Melt the butter, cocoa powder and the chocolate in a bowl over a pan of simmering water (bain marie).
Whisk the eggs and the sugar together. Once doubled in volume, gently fold in the chocolate, the flour and the hazelnuts.
Butter the silicone moulds and dust with flour. Pour the mixture into the moulds and cook in the oven for 10-12 minutes. Place straight into the fridge as soon they come out of the oven.
Remove from the moulds, allow to cool a little and then serve with the hot chocolate sauce.
Bring the cream to the boil, pour over the chocolate then whisk the butter in. Serve with the brownies.
«Feel free to replace the hazelnuts with other nuts, dried fruits or chocolate chips. You can also prepare this recipe in advance and gently reheat when ready to serve.»