Preheat oven to 160C. Melt both chocolates and butter in a heatproof bowl placed over a saucepan of simmering water, then set aside to cool slightly.
Whisk yolks, both sugars and vanilla in an electric mixer until pale and creamy (4-5 minutes). Stir into cooled chocolate.
Whisk eggwhite until stiff peaks form, then fold gently into chocolate mixture. Spoon into eight, 200ml (9cm-diameter, 4cm-high) non-stick moulds coated lightly with melted butter and sugar until three-quarters full, then place in a roasting pan and fill with enough boiling water to come halfway up sides of moulds. Bake until cakes are risen and set (40-45 minutes). Cool on a wire rack. Do not refrigerate - the cakes need to be served the day they're made. Serve with raspberries, blackberries and cherries.
Note Christine Manfield uses Valrhona
chocolate in this recipe.