Very lightly grease the moulds you’ll be using for your panna cotta.
Combine all the ingredients except for the vanilla and salt in a medium/large pot. Whisk to combine, then place on the smallest hob/burner over a medium-low heat.
Stir intermittently and continue to cook your cream mixture. You want it to reach a boiling point (vigorous small bubbles on the surface) without burning the mixture or heating it too quickly.
If the mixture has not reached this point after 10 minutes, turn the heat up a little.
Once the mixture reaches this point, keep it there for another minute or two.
Add the vanilla and salt and stir to combine.
Remove the mixture from the heat and carefully decant into a pouring jug. You can pass it through a sieve if any milk skins have formed.
Pour the mixture into your prepared moulds and allow them to cool for 10 or so minutes before transferring them to the fridge. Every batch is different, but allow 2-4 hours to cool and set. I recommend making them the night before so you can correct any issues that come up (see the notes below).
Serve with a sauce of your choosing or plain. Best eaten within a few days.