Puree half the strawberries in a blender and pass through a fine sieve.
Mix lemon juice into the sieved strawberry puree.
Slice the remaining strawberries and stir them into the puree.
Melt the grated white chocolate in a heatproof bowl over a pan of simmering water.
Soak the gelatine in 50ml of water for five minutes.
Simmer 112.5ml of cream with icing sugar and stir in the gelatine water until dissolved.
Stir the warm cream mixture and 75% of the strawberry puree into the melted chocolate.
Whip the remaining cream to soft peaks and fold it into the chocolate strawberry base.
Divide into glasses and chill in the fridge for at least two hours or overnight.
Serve topped with reserved puree, fresh strawberries, icing sugar, and mint sprigs.