Heat 9,150 ml of water with the sugar, mint and grated lemon peel until all of the sugar has dissolved in the liquid.
Then let the sugar solution boil over high heat without a lid. Some of the water evaporates, and in the end about 100 ml of syrup should remain in the pot.
This syrup is also known as sugar syrup. Let the sugar syrup cool down. Remove the lemon peel by straining it.
Prepare agar according to the instructions, add to the warm (not hot) sugar syrup and dissolve in it.
Puree the raspberries with a hand blender. Brush the raspberry mixture through a hair sieve so that it becomes nice and creamy and the seeds are removed.
Now add 1-2 tbsp raspberry mixture to the sugar syrup and stir. Then add this raspberry, sugar and mint mixture to the rest of the raspberry mixture and add lemon juice to taste.
It should be quite sweet, as the sweetness of frozen sorbet does not appear as sweet as when it is warm.
Place the raspberry sorbet mixture in the largest possible bowl in the freezer for 45 minutes. A layer of ice should form on the surface.
Beat the whole mixture vigorously with a large and sturdy whisk. Put the bowl back in the freezer.
Repeat this process two or three times with an interval of about 30 minutes.
The consistency of the sorbet depends on how often it is stirred. The more often it is stirred, the smoother it becomes.