Reduce sugar and water to a light syrup and allow to cool. Then puree with the cleaned berries and lemon juice. Depending on your taste, pass through a sieve.
Dissolve the gelatine according to the instructions and add to the puree.
Put the mixture in a very cool place. When the mixture begins to set, fold in the whipped cream.
Pour the mousse into serving bowls or glasses and place back in the refrigerator.
Fruit sauce:
Puree the other 250 g berries, the water, the sugar and the lemon juice with the hand blender and pass through a sieve (you can also use a little less water and add a little liqueur or schnapps instead).
Now whip the remaining 100 ml of cream until it is almost stiff.
Take the mousse out of the fridge and pour a layer of fruit sauce on top. Add a layer of the almost stiff whipped cream to the sauce.
Finally, garnish with a few berries and a mint leaf.