Place the cream in a saucepan. Halve the vanilla bean lengthwise; scrape out the seeds with a knife, then add the seeds and pod to the saucepan. Add the sugar and bring to a simmer over medium-low heat, stirring occasionally. Discard the vanilla pod.
Sprinkle the gelatin over the milk in a bowl and let stand until the gelatin softens, about 5 minutes. Stir the gelatin mixture into the hot cream mixture until dissolved, then stir in the yogurt. Divide among six to eight 4-ounce ramekins, cover with plastic wrap and refrigerate until set, at least 6 hours or overnight.
Dip each ramekin three-quarters of the way in warm water and invert onto a plate. Garnish each panna cotta with strawberries and mint, if desired.
Photograph by Jim Franco
Courtesy of Michael Symon for Food Network Magazine