Roll out the pastry on a lightly floured surface, then slice into three long strips. Line a baking tray with parchment paper. Transfer the pastry to the tray and prick all over with a fork. Refrigerate for 30 minutes.
Preheat the oven to 200˚C/180˚C fan/gas mark 6.
Brush the pastry with the beaten egg and bake for 15-20 minutes until the pastry is puffed and crisp. Set aside to cool at room temperature.
Beat the mascarpone and cream in a mixing bowl until smooth.
Beat in the icing sugar and orange zest until combined. Stir the jam and orange juice in a small bowl until combined.
Place one pastry sheet on a serving platter and spread over one-third of the jam mixture.
Top with one-third of the cream, then arrange one-third of the strawberries over the top.
Repeat these layers twice more. Finish with a sprinkling of flaked almonds and a dusting of icing sugar.