Split the vanilla rods. Pour the milk and the cream into a pan, add the vanilla rods, and heat to simmering point. Pull the pan off the stove, scrape the vanilla seeds into the milk, discard the rods. Cover and leave to rest.
Cream the sugar with the egg yolk a using electric mixer until light and fluffy.
Pour the luke-warm vanilla milk into the egg mixture while whisking constantly.
Cook over very low temperatures for about 15 minutes until you get a thick cream. Stir constantly and do not allow to boil!!!
When the cream coats the back of the wooden spoon, it is ready. Pour it into bowl or jug, cover and let it cool completely.
Transfer to an ice-cream maker and follow the instructions.
Alternatively pour the cream into a flat, frost-proof tray and place it in the freezer. After 2 hours whisk with a hand-held electric mixer. Repeat this every hour for 3 more times.