In a big bowl, whip the fresh cream, slowly adding the icing sugar until stiff. Put some of the whipped cream aside for decoration. Add the mascarpone cheese a little at a time and mix well. Cover and put in the refrigerator.
Combine the sugar and 100ml of water in a saucepan, stir over a low heat until the sugar dissolves. Bring to the boil. Add the strawberries and cook for 2 – 3 minutes. Remove from the heat, add the lemon juice and strain the syrup into a bowl and let it cool. Line a charlotte mould or pudding bowl (1 ltr capacity) with cling film. Cut a small piece at the end of each biscuit, dip each biscuit very quickly into the syrup and place round the mould with the cut end towards the top. Cover the bottom as well, cutting the biscuits to fit, where necessary. Do not dip all the biscuits at once in the syrup, as they will become too soft.
Put half of the well-drained strawberries on the bottom, cover with half the cream, then again with the strawberries, and finish off with the cream. Cover the top with more sponge fingers dipped in the syrup and cover with more cling film. Cover the charlotte with a plate that fits, place a weight on top and chill in the refrigerator overnight.
Unmould the charlotte, and decorate with more cream and strawberries on top.