While the dough is thawing to room temperature in a corner of the work-surface, clean and wash the strawberries. Cut them into pieces (if large) and leave to rest in a bowl sprinkled with lemon juice and dusted with sugar (2 spoonfuls). Roll out the dough on a napkin, and spread over the sheet in order; the crushed biscuits, sugar, raisins, cinnamon, strawberries, muesli, chopped chocolate, rum (sprinkled), grated lemon rind, small flakes of butter, vanilla and beaten egg with a pinch of salt. Roll the sheet up, with the aid of the napkin and put the roll into a greased oven-dish, brushed with egg and bake in a preheated oven at 425°F for about half an hour.