Place half of the strawberries into a blender and puree until smooth. Pass the puréed strawberries through a fine sieve into a clean bowl.
Add the lemon juice to the bowl.
Slice the remaining strawberries and add to the purée.
Place a heatproof bowl in a saucepan half-filled with boiling water. With the heat turned down very low, place the grated chocolate in the bowl and leave until melted.
In a small bowl, add the gelatine to about 50ml/¾ fl oz of water and leave to rest for five minutes.
Place a quarter of the cream along with all the icing sugar into a pan and simmer until warm. Add the gelatine water and stir for five minutes over a low heat until dissolved. It is important not to let the mixture boil, so keep the heat under the pan gentle.
Pour the cream and gelatine mix into the melted chocolate and stir until smooth. Add three quarters of the strawberry purée.
Place the remaining cream into a bowl. Whip the cream until soft peaks form when the whisk is removed from the bowl. Gradually fold the cream into the chocolate and strawberry mix.
Transfer the mixture to individual serving glasses. Place in the fridge to chill for at least two hours, preferably overnight (store the remaining strawberry purée in the fridge too).
To serve, add a spoonful of the remaining strawberry purée to each serving glass. Garnish with a few strawberries, dust with icing sugar and add a sprig of mint to each glass.