Put the pieces of white chocolate in a bowl, and sit this bowl over a pan over simmering water until it melts, stirring gently with a spatula every now and then. When it's melted, stand the bowl on a cold surface to cool down a little.
In another bowl, and using an electric handheld whisk for ease, whip the cream, egg white and extract together. You want soft peaking rather than a stiff mixture.
Put a big dollop of cream onto the slightly cooled chocolate and mix, and then gently fold the chocolate mixture into the cream.
Divide mixture between 6 small but perfectly formed glasses with a capacity of 60ml/ 1/4-cup each.
Chill in the fridge or give them a fast icy zap but sitting them in the deep freeze for 10 or 15 minutes. Decorate top with a mint leaf before serving.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.
Recipe courtesy of Nigella Lawson(Copyright 2007, Nigella Express, Hyperion, All Rights Reserved)