1. Sprinkle the gelatin over the cold water in a medium-sized bowl and let stand 5 to 10 minutes.
2. Heat the heavy cream and sugar in a saucepan or microwave. Once the sugar is dissolved, remove from heat and stir in the vanilla extract.(If using a vanilla bean, scrape the seeds from the bean into the cream and add the bean pod. Cover, and let infuse for 30 minutes. Remove the bean then rewarm the mixture before continuing.)
3. If you plan on unmolding the panna cotta later, then lightly oil eight custard cups with a neutral-tasting oil otherwise you can skip this step.
4. Pour the very warm Panna Cotta mixture over the gelatin and stir until the gelatin is completely dissolved.
5. Divide the Panna Cotta mixture into the prepared cups or wine goblets, then chill them until firm, which will take at least two hours (could take up to 4 hours depending on the temperature of your refrigerator).
6. To make the compote: Melt the butter in a medium saucepan or skillet over moderate heat. Stir in the sugar and lemon juice. Add the berries and tossing gently (to prevent them from completely breaking up) for about 2 to 3 minutes (until berries are warm and juices begin to release).
7. When ready to serve the panna cotta, spoon the compote over. If you plan on unmolding, run a sharp knife around the edge of each panna Cotta and unmold each onto a serving plate, and top with the mixed berry compote.
If you’re pressed for time, pour the Panna Cotta mixture into wine goblets so you can serve them in the glasses, without unmolding.
6. Run a sharp knife around the edge of each Panna Cotta and unmold each onto a serving plate, and garnish as desired.