Add the custard to a bowl. Roughly chop the chocolate and place in a heatproof bowl. Melt over a pan of simmering water, or in the microwave.
Beat the melted chocolate into the custard with a good pinch of salt and divide between ramekins or glasses.
Allow to set in the fridge for a minimum of 3 hours, overnight if easier.
Whip the crème fraîche with a whisk until it holds a soft peak. Spoon over the chocolate pots and scrunch over the pistachios.
