Preheat oven to 190c
Take the block of puff pastry. Cut it in half and shape 2 exact rectangles
Place each pastry square on a lined baking sheet, brush with beaten egg and bake for 25 minutes. Dust with icing sugar and leave to cool
Whip the double cream to soft peaks and fold into the custard.
Mix the raspberries and strawberries together with 1 tbsp caster sugar and allow to sit for at least half an hour.
Cut the pastry in half horizontally so that you have 2 crispy layers of puff.
Place one layer on a plate or board, spoon over the custard and sprinkle the berries on top. Top with the prettiest pastry top and serve.