Chocolate Panna Cotta: Soak the gelatin sheet in ice-cold water.
Cut the vanilla pod lengthwise and scrape out the seeds.
Put the cream, sugar, vanilla seeds, and the pod in a saucepan and gently bring to a boil while stirring.
Remove the pan from the heat as soon as it boils and take out the vanilla pod. Add the chocolate and let it melt while stirring. Then add the squeezed gelatin and stir well.
Strain the mixture into a measuring cup and let it cool slightly.
Place 4 glasses at an angle on a baking sheet that fits in the refrigerator (e.g., by using egg cartons or cupcake molds to keep them tilted). Pour the chocolate panna cotta into the glasses and let it set for 2 hours in the refrigerator.
Pistachio Panna Cotta: Soak the two sheets of gelatin in ice-cold water.
Heat the cream and sugar in a saucepan while stirring until it just boils.
Add the squeezed gelatin and stir well, followed by the pistachio paste. Blend the mixture with an immersion blender for a smooth texture and strain it into a measuring cup.
Let it cool and set the glasses upright once the chocolate layer has set. Pour the pistachio panna cotta over the chocolate layer and let it set again for 2 hours in the refrigerator.
Chocolate-Nut Crunch: Chop all the ingredients for the crunch finely in a food processor.
Store the crunch in an airtight container until you are ready to serve.
Finishing: Serve the panna cotta with a spoonful of nut crunch on top, a sprig of mint, and a slice of mandarin or orange. Edible flowers add an extra festive touch.