Into a saucepan over medium heat add the milk, 50g of the sugar and the seeds and pod of the vanilla bean.
Bring the milk to just below a boil, where it is steaming rapidly. (If you have some time remove from heat and allow the vanilla to infuse for 20 minutes, then bring back up to temperature)
In a separate bowl add the egg yolks and the remaining 50g sugar. Whisk until pale and fully incorporated together.
Whilst whisking the eggs, add a little of the hot milk, whisk until mixed, then add some more milk. Continue until all the milk is incorporated.
Wipe out the saucepan, and strain the milk and egg mix back into the saucepan. Discard, including the vanilla seed pod.
Place on medium heat and with a wooden spoon, stir continuously until the custard changes consistency and thickens to coat the back of a spoon. (if you have a thermometer don’t let it go above 84C or it will scramble the eggs)
Remove from heat and cover the custard with a ca-touche. That is a piece of plastic or silicon paper pressed onto the surface of the custard to prevent a skin forming.
Once cooled down to room temperature, place in the fridge. Chill for 4 hours or overnight. Will make 600ml custard