Soak the gelatine in a small bowl of cold water for 2 minutes then gently squeeze out the water. Place in a heatproof bowl with the lemon juice. Stand the bowl in a saucepan of hot water and heat gently stirring until the gelatine dissolves. Remove from the heat.
Push the raspberries through a nylon sieve to make a seedless purée, reserving 6 raspberries to decorate.
Whip the cream until just standing in soft peaks. Fold the cream into the raspberry purée, then add the dissolved gelatine.
Whisk the egg whites until standing in soft peaks. Gradually whisk in the caster sugar, and fold into the raspberry cream mixture.
Spoon into serving dishes and pop a raspberry into the centre of each. Chill for at least 2 hours or until set.