Soak the gelatine in cold water. Set aside a few strawberries for decoration.
Wash and puree the remaining strawberries. Stir sugar and lemon juice into the fruit puree until the sugar is dissolved. Heat 6 tablespoons of the puree, squeeze out the gelatine and dissolve in it. Then stir the dissolved gelatine into the rest of the berry mixture and let it cool down. As soon as the cream has set, whip the cream until stiff and fold in. Pour into a bowl and chill overnight.
Turn out before serving and garnish with quartered strawberries, pistachios and lemon balm.