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 or mint, or
Coulis if desired.