Put the frozen berries into 4 ovenproof moulds and sprinkle with sugar. Sprinkle with liqueur and let thaw at room temperature for about 1 hour. Whip the cream until stiff. Separate the egg.
Mix the egg yolks and 3 tablespoons of milk. Beat the egg whites until stiff. Boil up the rest of the milk. Remove the pan from the heat, add the semolina pudding and egg yolk to the milk at once, stirring with a whisk, and continue stirring vigorously for about 1 minute, but do not put it back on the heat.
Add the egg whites and cream and spread the semolina foam on the berries. Bake in the preheated oven (electric range: 225°C/ gas: level 4) for 10-15 minutes. Serve sprinkled with icing sugar and lemon balm.