In a small bowl, sprinkle the gelatin on 3 tablespoons of cold water. Stir and set aside for 10 minutes to allow the gelatin to dissolve.
Meanwhile, in a medium bowl, whisk together 1½ cups of the cream, the yogurt, and vanilla extract. Split the vanilla bean and use the tip of a knife to scrape the seeds into the cream. Heat the remaining 1½ cups of cream and the sugar in a small saucepan and bring to a simmer over medium heat. Off the heat, add the softened gelatin to the hot cream and stir to dissolve. Pour the hot cream-gelatin mixture into the cold cream-yogurt mixture and stir to combine. Pour the into 8 (6- to 8-ounce) ramekins or custard cups and refrigerate uncovered until cold. When the panna cottas are thoroughly chilled, cover with plastic wrap and refrigerate overnight.
Thirty minutes to an hour before serving, combine the strawberries, balsamic vinegar, sugar, and pepper. Set aside at room temperature.
To serve, run a small knife around each dessert and dip the bottom of each ramekin quickly in a bowl of hot tap water. Invert each ramekin onto a dessert plate and surround the panna cotta with strawberries. Dust lightly with freshly grated lemon zest and serve.
Copyright 2006, Barefoot Contessa at Home by Ina Garten, Clarkson Potter/Publishers, All Rights Reserved