For chocolate cream, place the chocolate in a heatproof bowl, whisk the custard powder, sugar and egg yolks until smooth in a medium bowl.
Bring the milk to the boil in a medium saucepan, slowly pour the hot milk into the egg mixture, whisking continuously.
Pour the custard back into the saucepan and cook over medium heat until the mixture boils and thickens, whisking continuously.
Pour the mixture over the chocolate, whisking until combined then whisk in the butter until combined.
Transfer to a container, covering the surface with clingfilm and refrigerate for at least 2 hours.
Preheat the oven grill, cut grapefruit in half and carefully cut through each segment and around the peel (this will make accessing the grapefruit easier).
Place cut side down onto paper towel for ten minutes.
Place grapefruit onto a foil lined oven tray, sprinkle each grapefruit half with a tablespoon of sugar in an even layer and place under the grill.
Cook for 15 minutes or until caramelised. Set aside for five minutes to cool.
Serve with a dollop of chocolate cream, drizzled with creme fraiche and sprinkled with pistachio.
