Rehydrate the gelatin sheets in a generous amount of very cold water for about 10 minutes. Make sure they are fully submerged.

In a saucepan, combine the cream, milk, granulated sugar, and vanilla sugar. Place over medium heat.

Stir occasionally to help the sugar dissolve. Remove from heat as soon as the mixture starts to rise. Do not let it boil to avoid forming a milk skin.

Add the well-drained gelatin and stir until fully dissolved.

Pour the mixture into serving glasses, leaving space at the top for the raspberry coulis layer. Let sit at room temperature for around 45 minutes, or until no steam is rising.

Refrigerate for at least 6 hours, preferably overnight, until the panna cotta is fully set.

Prepare the coulis once the top of the panna cotta is set and no longer wobbly.

Rehydrate the gelatin in a bowl of cold water for 10 minutes.

If you're using fresh raspberries, blend them and strain through a fine sieve to remove the seeds.

In a saucepan, combine the strained coulis and sugar. Heat gently, just until the sugar is fully dissolved.

Remove from heat and stir in the well-drained gelatin until completely dissolved.

Gently pour the coulis over the set panna cotta in the glasses. Let it cool slightly before placing back in the refrigerator to allow the coulis to set.

Decorate with a raspberry before serving.