Whisk the milk, cocoa and pistachio cream together in a small saucepan until combined, then heat gently until small bubbles form around the edges and the milk is hot but not boiling.

Just before the milk boils, remove the pan from the heat and stir in the grated chocolate. It should melt in the residual heat, but if not, return the saucepan to the stove over a low heat and gently melt the chocolate.

To make the pistachio whipped cream, whip the cream to soft peaks using a balloon whisk and then swirl in the pistachio cream to create a marbled effect. You may need to heat the pistachio cream briefly if it is a little thick – you want it to easily drizzle off your spoon into the cream.

Divide the hot chocolate between two mugs or heatproof glasses, then top with pistachio whip and sprinkle with chopped pistachios to serve.