In a small bowl add the water and then sprinkle the gelatin over the top and let it sit undisturbed for 5 to 10 minutes.
In a medium sized bowl, whisk together 1/2 cup of the cream, 1 cup yogurt, the vanilla and the salt. Let the yogurt mixture sit while you heat the remaining 3/4 cup cream and 1/3 cup sugar in a small pot over medium-low heat, stirring occasionally until the sugar is dissolved and the mixture is just starting to bubble gently (not boiling).
Remove the pot from the heat and scrape in all of the gelatin mixture, stirring until completely dissolved (no granular texture, it should be smooth). Then add this gelatin-cream mixture to the yogurt mixture and whisk together thoroughly.
Ladel mixture into 6-ounce molds (anything works; small bowls or ramekins). Refrigerate until set (4 hours or up to 3 days). Only cover with plastic wrap after they are cold to avoid condensation.
About an hour before serving, make the strawberry sauce by first slicing up 2 1/2 cup strawberries (I used frozen berries that were thawed) and placing them in a medium bowl. In a food processor puree the remaining 1/2 cup berries with 2 Tbsp sugar and 2 tsp lemon juice. Add the puree to the sliced berries and stir in 2-3 Tbsp balsamic vinegar, 1/4 tsp pepper and a pinch of salt. Let sit for 30 to 60 minutes.
When ready to serve, dip ramekins or molds into hot water for a few seconds, Run a thin, sharp knife around inside of mold and then invert panna cottas onto individual dessert plates. Shake to loosen, or tap bottoms of mold and then lift off ramekins or molds. Spoon strawberry sauce over each panna cotta. Serve immediately.