Let the raspberries thaw. Meanwhile peel the mangos, remove the flesh from the core and puree very finely with the cutting stick of the hand mixer. Stir in 1 tablespoon of icing sugar and lemon juice and fill into a wide metal bowl. Puree raspberries as well. Stir in the remaining icing sugar and arrack, fill into a wide metal bowl and place in the freezer together with the mango puree for at least 5 hours.
Stir vigorously with a whisk about every half hour. It is best to pre-freeze glasses. Layer mango and raspberry sorbet alternately. Decorate with lemon balm