1. Bloom the powdered gelatin in the cold milk and allow to sit for about 5 minutes.
2. In a medium-sized bowl, whisk together the sugar, salt, Greek yogurt, and seeds from the vanilla bean. Mix until smooth.
3. Incorporate approximately ⅔ of the heavy cream into the yogurt mixture.
4. In a small saucepan, warm the remaining heavy cream with the bloomed gelatin until warm to the touch.
5. Quickly whisk the dissolved gelatin mixture into the yogurt mixture.
6. Immediately deposit the panna cotta into cups of another similar vessel. If the panna cotta becomes too thick to pour, rewarm it over a pan of simmering water.
7. Chill for at least 2 hours before serving.
8. Serve with macerated berries, candied nuts, or similar accompaniments.