Split the vanilla pods and scrape the seeds into a bowl with the sugar. Add the egg yolks and beat with a whisk until stiff.
Scald the cream by bringing it slowly to the boil with the vanilla pods in it, then pour on to the egg mixture, whisking vigorously.
Return to a clean saucepan and cook over a low heat, whisking all the time. As it starts to thicken, change to a wooden spo