First, put the gelatin sheets in a bowl of cold water until fully submerged. Add them one by one so they don’t stick together. Let them sit for about 10 minutes.
Meanwhile, pour the cream into a saucepan and add the sugar and vanilla (if you use a vanilla bean, carefully cut it open lengthwise and scrape the seeds out with the knife).
Turn the heat to medium-low and bring the cream almost to a simmer. It should be hot but not boiling and the sugar should be completely dissolved.
Turn off the heat and add the freshly brewed espresso coffee to the cream.
Squeeze the gelatin sheets to remove the excess water and add them to the cream as well. Mix well until all the ingredients are fully incorporated.
Pour the cream into silicone molds or serving cups, then set them aside to cool completely.
Put the cooled Panna Cotta in the fridge for 2-3 hours until fully set.
Optional: Melt the dark chocolate in the microwave and spoon it over the set and de-molded panna cotta. Place them again in the fridge for 15-20 minutes to solidify.
Serve cool or at room temperature. Decorate with chocolate ribbons, sprinkles, or chocolate-covered coffee beans.
Notes
Sugar: You can use either caster sugar, regular granulated sugar, or raw brown sugar in the same quantity.Gelatin: In my case, 8 g/0.3 oz corresponds to 5 sheets of gelatin, but the weight may differ by brand. Check the weight per sheet on the box and calculate to get the right amount. Alternatively, you can use 2 ½ teaspoon of gelatin powder to replace the sheets. Add the gelatin powder to the hot cream at the same time as mentioned in the recipe and mix well to make sure it’s fully dissolved.Vanilla: You can substitute the vanilla bean with 1 teaspoon of vanilla extract or ½ teaspoon of vanilla powder.How to easily de-mold the panna cotta from the silicone mold: First, with a knife gently and carefully detach the panna cotta from the mold's borders. Then place the silicone mold in hot water for a few seconds and flip it onto the serving plate. If it doesn't come out immediately, repeat the steps again. (Do not let it sit too long in hot water or it will melt.)How to store: Panna cotta will keep up to 3 days in the fridge. Cover it with plastic wrap to avoid any flavor alteration. If needed, it's also possible to freeze panna cotta for up to 3 months. Keep in mind, though, that freezing may alter the texture and flavor.