In a medium saucepan, combine the cream, sugar, vanilla bean paste, (or the scraped vanilla bean, and seeds) and lemon zest (also add the optional rosemary sprigs at this point, if using). Heat the mixture over medium heat until it’s just beginning to simmer. Remove from the heat, cover, and let steep for 15 minutes.

After 10 minutes, place the ¼ cup of water in a small microwave-safe bowl. Sprinkle the gelatin over the water and let it sit for 5 minutes until evenly moistened. At this point, the mixture will be thick and opaque.

Place the bowl with the gelatin mixture in the microwave and cook for 30 seconds on high power. Stir to make sure all of the gelatin is dissolved. The mixture should now be thinned out and clear.

Bring the cream mixture back to the simmering point over moderate heat. Remove from heat, add the gelatin/water mixture and stir well. If you used a whole vanilla bean pod, remove it now and discard.

Divide the panna cotta mixture between six small ramekins, glass jars, bowls cocktail glasses. Cover with plastic wrap and refrigerate for at least 6 hours (or up to 48 hours).