Sprinkle the gelatin over 2 tablespoons of the water in a small bowl and let stand until the gelatin is softened, about 5 minutes. In a medium-size saucepan, bring the milk, ½ cup of the sugar, and vanilla bean to a boil. Immediately remove the saucepan from the heat. Scrape the gelatin mixture into the milk and stir until dissolved. Remove the vanilla beans and, with a pairing knife, scrape the seeds into milk. Strain the milk mixture into a medium-size bowl and cool to room temperature. Meanwhile, prepare the caramel-lined molds. Have six 8-ounce ceramic ramekins near at hand before starting the caramel. In a small, heavy saucepan make a caramel with 1/3 cup sugar and 3 tablespoons water. Immediately pour the caramel into the ramekins, dividing it evenly. Set the prepared ramekins aside, remembering that they will retain the heat for several minutes. In a medium-size bowl, beat the heavy cream with an electric mixer until it forms stiff peaks when the beaters are removed. Add the whipped cream to the milk mixture and fold the two together with a rubber spatula. Divide the whipped cream mixture among the caramel-lined ramekins and place in the refrigerator. Chill until firm, at least 2 hours, or up to one day. To serve, invert the ramekins onto serving plates. Wait a moment until the caramel sauce begins to seep onto the plate. Lift the ramekin. Decorate with the frutte di bosco and mint sprigs and serve immediately. Note: Frutta di bosco can be any assortment of fresh, seasonal fruit, but berries are especially nice with panna cotta. To use other ripe, soft fruits, such as cherries, peaches or apricots, just remove the stones and peels as necessary and cut them into thin slices or bite-size pieces.