Method

• 1.
  For the pastry cream, whisk the egg yolks, sugar, lemon zest, plain flour, cornflour and 2 tablespoons milk together in a bowl until smooth. Place remaining milk in a pan over medium heat and bring to just below boiling point. Gradually whisk hot milk into yolk mixture, then return mixture to a clean pan. Cook over low heat for 6 minutes, whisking constantly, until smooth and thick. Spoon into a bowl and cover the surface closely with plastic wrap to prevent a skin forming. Chill for at least 1 hour.
• 2.
  Line 3 trays with baking paper. Roll each pastry sheet out to make thin 30cm squares, then cut in half. Place 3 pastry halves on the baking trays and chill for 20 minutes. (The remaining piece can be re-frozen in plastic wrap for future use.)

• 3.
  Preheat the oven to 200°C.
• 4.
  Brush the eggwhite over the top of the pastry rectangles, leaving a 1cm border and taking care not to let any run over onto the edges (this will prevent it from puffing up). Sprinkle the caster sugar evenly over each piece and scatter with the flaked almonds. Bake for 20 minutes or until risen and golden. Remove from the oven, then use the back of a baking tray to gently flatten the pastry. Transfer to wire racks to cool.
• 5.
  Shortly before serving, beat the pastry cream to loosen it a little, then beat in the orange zest. Whip the thickened cream to soft peaks and gently fold into the pastry cream until combined.
• 6.
  Place 1 piece of pastry on a platter (saving the best-looking one for the top) and spread with half the pastry cream. Repeat each layer, then top with the reserved pastry top. Dust liberally with the icing sugar. Slice across with a sharp serrated knife and serve.