Whisk the eggs, sugar, milk, cream and salt in a bowl over a pan of simmering water until it reaches around 75C.
Remove the bowl from the heat and add the chocolate (or you can sieve the mixture over a jug of chocolate).
Let it sit for 2 minutes then whisk it or use a hand blender until smooth.
Cover the surface of the cremeux and chill for 6 hours or overnight, then use! Don’t whisk it, you can use it straight from the fridge.