For the crème pâtissière

• 250 ml/9 fl oz milk
• 1 vanilla pod, split lengthways

First make the crème pâtissière. Put the milk in a saucepan with the vanilla pod and heat gently to boiling point. Whisk together the egg yolks, sugar and flour. Pour the hot milk on to the egg mixture and whisk lightly together. Return the mixture to the saucepan and cook gently until it thickens. Pour through a sieve, discard the vanilla pod and chill.

For the chocolate mixture, cream