Place 6 serving glasses in the fridge so they are well chilled before you pour in the panna cotta mixture. This helps the dessert cool evenly and set with a smooth surface.

In a small bowl, sprinkle the gelatine powder over the cold water. Leave it to stand for a few minutes until the granules absorb the liquid and swell; this blooming step ensures the gelatine will melt smoothly into the warm mixture later.

Add the milk, vanilla extract (or split vanilla pod and seeds), and sugar to a small saucepan. Set over medium heat and warm gently, stirring often, until the sugar has completely dissolved and the milk is fragrant with vanilla. The mixture should be hot but not boiling—remove the saucepan from the heat just before it reaches a simmer.

Scrape out and discard the vanilla pod if using. Add the bloomed gelatine to the hot milk mixture, whisking steadily until the gelatine has fully dissolved and no granules remain.

Slowly pour in the cold cream, stirring as you add it so the mixture becomes smooth and well combined. Let it sit for about 5 minutes to cool slightly; this brief rest helps prevent the cream and milk from separating in the glasses.

Retrieve the chilled glasses from the fridge and carefully pour the panna cotta mixture into each one, dividing it evenly. Return the glasses to the refrigerator and allow the panna cotta to chill until completely set—this will take at least 5 hours, but overnight is ideal for the best texture.

For the berry coulis, place the strawberries or frozen berries and sugar into a small saucepan. Bring to a gentle simmer over medium heat and cook for about 5 minutes, stirring occasionally, until the berries soften and release their juices and the sugar has dissolved. Remove from the heat and let the mixture cool, then transfer to a container and store in the fridge until needed. You can leave it slightly chunky or blend it for a smoother sauce.

When ready to serve, check that the panna cotta is firm and has a delicate wobble when the glass is gently moved. Spoon a layer of the chilled berry coulis over the top of each panna cotta, letting it spread naturally. Finish with a few fresh berries on top or on the side of the plate for a bright, elegant presentation.