Choose elderflowers with clean, creamy white petals, snipping the stalk just before the flowers fan out. Put in a large pan with the sugar and 550ml water, the lemon juice and the juiced halves of the lemons. Bring to a gentle simmer, then turn off the heat and leave to infuse (and the sugar to dissolve) for at least 1 hr or up to 5 hrs.

Line a large sieve with muslin and set over a bowl or pan. Strain the mixture and discard the flower heads and lemons. Pour into a freezeable container (preferably one with a lid) and freeze for 2-3 hrs until semi-frozen.

Scrape the semi-frozen mixture into a food processor or blender and blitz to break down the lumps of ice – you may need to scrape down the sides a few times. Put the sorbet back in the container and freeze for another 1-2 hrs.

Repeat this process another two or three times. The more times you blend the sorbet, the smoother it will be. Will keep frozen for up to three months. To serve, remove from the freezer and leave to stand for 5 mins before scooping.