For the Panna Cotta : Soak the gelatin leaves in a little cold water until soft.
Place the milk, cream, vanilla pod and seeds and sugar into a pan and bring to a slow simmer. Remove the vanilla pod and discard
If you are using vanilla extract, add it to the other ingredients directly.
Squeeze the water out of the gelatin leaves, then add to the pan and take off the heat. Stir until the gelatin has dissolved. If you are using powder, just add directly.
Divide the mixture among four bowls and leave to cool. Place into the fridge for at least an hour, until set.
For the Sauce : Place the sugar, water and mango into a pan and bring to the boil. For adding vanilla flavor, add 1-2 tsps of vanilla sugar.
Reduce the heat and simmer until the sugar has dissolved.
Take the pan off the heat and using a hand blender, blend the sauce until smooth.