1. Soak gelatine sheets in a bowl of very cold water for 5–10 minutes, until flexible and softened.
2. In a saucepan, combine cream, milk, sugar, and vanilla. 
3. Heat on low, stirring so the sugar dissolves fully.
4. Keep heating until you see small bubbles around the edges.
5. Avoid a rolling boil, which can affect texture.
6. Remove the pan from the heat as soon as it just simmers.
7. Squeeze excess water from the gelatine (don’t crush it completely dry) and add to the hot vanilla cream.
8. Stir for 30–60 seconds until there are no bits left.
9. If needed, warm for 10–15 seconds on very low heat (do not boil) to finish dissolving.
10. Divide between 4 small glasses or ramekins. Optional: strain through a fine sieve if you’re worried about tiny gelatine specks.
11. Let cool to room temperature, then cover and refrigerate until fully set.

Make the raspberry coulis

1. Add the raspberries (fresh or frozen), water, and sugar to a saucepan.
2. Bring to a gentle boil, stirring, until the sugar has fully dissolved and the mixture has slightly reduced.
3. Blend or mash into a smooth purée.
4. Strain through a fine sieve to remove the seeds.
5. Let the coulis cool completely, then spoon it over the panna cottas just before serving.