Reserve a few whole Black Currants for decoration.
Press the rest through a sieve into a measuring jug, then make up the puree to 1/4 pint with water.
Combine the Black Currant puree, sugar and lemon juice in a mixing bowl.
Place 2 tbsp water in a small heatproof bowl and sprinkle the gelatine on to the liquid.
Stand the bowl over a saucepan of hot water and stir the gelatine until it has dissolved completely. Cool slightly.
Fold a little of the Black Currant puree into the cooled gelatine, then whisk this mixture into the bowl of Black Currant puree.
Leave in a cool place until the mixture starts to set.
In a deep bowl, whip the cream until it just holds its shape, then fold into the Black Currant mixture with a metal spoon
Whisk the egg whites in a clean, grease-free bowl, and fold in.
Make sure that the mixture is thoroughly and evenly blended but do not overmix.
Pour gently into a glass dish, a wetted 17 fl oz mould or individual glasses.
Refrigerate for 1 - 2 hours until set, then turn out if necessary and decorate with whipped cream and the reserved Black Currants.