Heat the cream: Pour the milk into a saucepan and bring it to simmer.
Pour over chocolate: Once it starts to foam bubbles add the white chocolate into the boiling milk. Keep stirring until the chocolate properly.
Add the 30g unsalted butter: Add unsalted butter into the mixture of white melted chocolate and milk. Mix everything well.
Add vanilla flavor and Salt: Add 1 tsp of vanilla flavour and a dash of salt together. Combine everything for 8 to 10 minutes.
Cool and store: Let the sauce cool for a few minutes before using, since it will thicken slightly as it cools. Pour into a jar or squeeze bottle for storage.