To begin, make the lavender marshmallow as the syrup will need to rest overnight.
Bring the water and sugar to the boil in a saucepan and bring to the boil
Once the sugar has dissolved, remove from the heat and add the lavender. Allow to infuse for 30 minutes, then pass through a sieve. Soak the gelatine in cold water
Add the mashed raspberries to the pan and bring the mixture to the boil. Squeeze any excess liquid from the gelatine and stir into the raspberry mixture until fully dissolved. Allow to cool before placing in the fridge overnight
The next day, transfer the mixture to a blender and blitz until foamy. Pour into a baking tray lined with cling film and place in the freezer to set