Soak gelatine in cold water. Halve white grapefruits, squeeze juice. Measure out 100 ml of juice. Separate eggs. Mix the egg yolks, 3 tablespoons of hot water and sugar and beat over a hot water bath with a whisk until thick and creamy. Squeeze gelatine and dissolve in the hot egg cream. Stir in the juice.
Chill the cream until it begins to gel. Beat the egg whites until stiff and fold into the cream. Pour cream into glasses and chill for about 2 hours. Peel pink grapefruit so that the white skin is completely removed. Remove the fillets between the parting skins. Wash lemon balm and pat dry. Decorate cream with grapefruit fillets and lemon balm