To Prepare the Panna Cotta

1. In a small bowl, add 3 tablespoons cold water. Sprinkle the gelatin powder on the water, and stir to combine. Let sit for 10 minutes to allow the gelatin to fully dissolve.
2. In the meantime, in a medium bowl, whisk together half (1½ cups) of the heavy cream, the yogurt and the vanilla extract – mixing well to combine. Remove the seeds from the vanilla bean (cut the bean lengthwise with a sharp knife and then use the tip of the knife to scrape the seeds out of the bean); add vanilla seeds to the cream mixture.
3. In a small pan, heat the other 1½ cups of heavy cream and the sugar over medium heat. When the mixture comes to a simmer, remove from the heat and stir in the dissolved gelatin. Stir until completely dissolved. Add the hot cream-gelatin mixture to the cold cream mixture and mix well.
4. Pour the mixture into ramekins or custard cups (or a single, wide flat bowl will also work if you do not have ramekins) and chill until cold. Once the panna cottas are completely chilled, cover with plastic wrap and refrigerate overnight (or at least another 6 hours).
5. To Prepare the Balsamic Strawberries
6. Approximately half an hour before serving the panna cotta, in a bowl, combine the sliced strawberries, balsamic vinegar, sugar and black pepper. Let the mixture sit at room temperature to allow the flavors to combine.

To Serve

1. To serve the panna cotta, run the tip of a sharp knife around the custard in the ramekin and dip the bottom in a shallow pan of hot water to loosen the custard from the bottom of the dish. Place a dessert plate tightly over the ramekin and carefully invert the dessert so that the custard comes out of the ramekin. (Shake the ramekin gently if necessary to get the panna cotta out.)
2. Serve each panna cotta with the balsamic strawberries and a sprinkling of grated lemon zest on top.