I made this panna cotta in ramekins, but espresso cups are a good option for presentation flair. I’ve never unmolded my panna cotta, but if you wish to do so, my research indicates you can lightly oil the ramekins or dampen them with water before filling, and then run a knife around the edge before turning out the set pudding. Not having tried either of these methods, I wish you good luck (and let me know how it goes!).
Set six ramekins or other serving cups that will hold 4 fluid ounces on a baking tray or pan and set aside.
Gently melt the chocolate in a double boiler. I just set a heat-proof bowl over a pan of water that was first heated to a boil and then kept at a low simmer. You could also use the microwave. In either case, set it aside once melted.
While the chocolate is melting, put the cream, sugar and vanilla into a saucepan over medium heat and whisk until the sugar is dissolved. When the cream is just starting to shimmer, turn the heat as low as it will go and simmer for a few more minutes.
In the meantime, sprinkle the gelatin over ¼ cup cold water. Let it sit for a few minutes (this is called blooming, by the way), then add ¼ cup boiling water and stir until the gelatin is dissolved.
Whisk the warm melted chocolate into the cream mixture. Then add the gelatin mixture, stir well and carefully decant into the ramekins. Wipe away any dribbles or splashes (unless your decanting skills are much better than mine and it's not necessary) and place the tray of ramekins into the fridge to set for at least four hours.
You can make the panna cotta a day ahead. If refrigerating longer than four hours, wrap well with plastic wrap.
Garnish with the grated chocolate and prepare yourself to graciously accept the ooh’s and aah’s.