Sprinkle gelatin over water and bloom for 10 minutes.
Bring heavy cream, vanilla bean and seed, and sugar to a bare simmer, stirring to dissolve sugar; remove from heat. Add gelatin/water mixture to hot cream mixture; stir to dissolve. Whisk in buttermilk and strain through fine mesh strainer.
Immediately pour into 4 ounce ramekins and refrigerate until set, 4 hours or overnight.
Serve in ramekin or up-end and serve like a flan with fresh seasonal fruit.