In a wide bowl, sprinkle the gelatine over the milk and set aside to allow the gelatine to bloom.

Puree the thawed raspberries in a blender, then strain the mixture into a saucepan to remove seeds.

Add the sugar to the raspberry puree and warm over low heat, stirring until the sugar dissolves. Avoid letting the mixture bubble.

Stir the gelatine mixture into the warm raspberry puree, ensuring it dissolves completely. If necessary, press any undissolved bits against the side of the pan to break them up.

Strain the mixture once more into a bowl and let it cool to room temperature.

Whip the cream to soft peaks using a hand mixer, then gently fold it into the raspberry mixture in three separate additions.

Spoon or pipe the mixture into glasses or bowls, then refrigerate for at least 2 hours to set.

For the topping, heat the remaining raspberries and sugar in a small saucepan over low heat, stirring until the sugar dissolves. Let it bubble gently for 30 seconds before transferring to a small pitcher to cool.

Once the mousse has set, drizzle the cooled raspberry sauce over the top before serving.