In a small bowl add the cold water. Sprinkle the gelatin on top of the water and then give it a stir. Set aside while preparing the rest of the ingredients.
In a large bowl (I use a large glass bowl that has a spout on it for ease of pouring), stir together with a whisk or large spoon 1 cup of the half & half (the remaining 1/2 cup will be used in the next step), yogurt, vanilla extract, vanilla bean seeds and pinch of salt.
Add to a small saucepan the remaining 1/2 cup of half & half and the sugar. Cook on medium low heat and continue to stir until it comes to a low simmer and the sugar is completely dissolved.
Add the gelatin mixture to the pan and stir until combined (the mixture will look like applesauce when combined).
Add the contents of the pan to the large bowl mixture and stir with a whisk or large spoon until combined.
Pour panna cotta into 6 containers (4 ounces each).
Refrigerate uncovered for about an hour until the panna cotta is set. Once it is set, cover with plastic wrap until time to garnish and serve.
Add the mango compote or other garnish right before serving.