Here is the recipe you wanted from Josceline Dimbleby's Sweet Dreams book.
Christopher’s Bombe Surprise
Serves 8
2 large egg whites
Juice of 3 lemons
6 oz (175g) of caster sugar
1 teaspoon (5ml) of gelatine
1/2 pint (300ml) of whipping cream
6 oz (175g) plain chocolate, grated of chocolate...