Bring the milk and cream to a boil, in a medium saucepan.
Slice the vanilla pod lengthways and scrape out the seeds with the back of a knife. Add the seeds to the saucepan along with the pod.
In a medium sized heat-proof bowl, beat the egg yolks with the sugar until thick and pale.
When the milk and cream have come to a boil, remove the vanilla pod and pour 1/3 into the egg mixture, whisking until thoroughly combined.Then pour the egg mixture into the saucepan with the remaining milk and continue whisking. (Whisking is important otherwise the custard may catch and burn in the saucepan.)
Once the mixture has thickened, remove it from the heat and pour it into a clean bowl. DO NOT LET IT BOIL, or the eggs will scramble.
Cover with cling film, lightly pressing it against the surface to prevent a skin from forming. Serve with your favourite dessert or leave to cool.