Whisk the cornflour and egg yolks together in a bowl or jug. Pour the milk and half the cream into a second jug and set both aside.

Melt the butter in a large saucepan over a low heat with the sugar until the sugar has melted, about 2-3 mins. Turn up the heat to medium and simmer for 1-2 mins to bring out the caramel flavours, being careful not to burn the sugar. Remove from the heat and gradually whisk in the cream mixture. Do this slowly and carefully, as the hot sugar mixture may spit a little.

Return to the heat and bring to a simmer, whisking continuously. Remove from the heat and spoon 3-5 tbsp into the egg yolk and cornflour mixture to loosen slightly, then tip it all into the saucepan, and whisk everything together. Return to a medium heat, whisking until the mixture comes to a simmer and begins to thicken into a custard. Remove from the heat and pour into four or six serving glasses or ramekins, then chill for 4 hrs or overnight until set.

Just before serving, whisk the remaining 150ml cream to soft peaks using an electric whisk, and pipe or spoon this over the puddings. Grate over some chocolate to serve, if you like.