Pastry:

1. Preheat oven to 180ºC (350ºF). Line trays with baking paper.
2. Place pastry sheets flat, prick with a fork, cover with baking paper, and weigh down with another tray.
3. Bake 20–25 minutes until golden. Cool completely on racks.
4. Trim to fit a 9×13 inch (23×33 cm) cake tin.

Custard:

1. Heat milk, cream, butter, vanilla, and sugar in a saucepan until just boiling. Remove from heat.
2. Whisk Cornflour, custard powder, and water together.
3. Whisk this into the hot milk mixture with the yolks.
4. Return to heat, whisking until custard boils and thickens (about 1 min).
5. Strain for smooth texture.

Assembly:

1. Line a cake tin with foil (overhanging). Place one pastry sheet inside.
2. Spread custard evenly, top with the second pastry sheet, and press gently.
3. Chill 3–4 hours until set.
4. Dust with icing sugar, slice with a hot serrated knife, and serve.

Notes:

1. Best eaten within 1–2 days. Pastry softens in the fridge but stays tasty.
2. Leftover egg whites can be frozen or used for pavlova/meringues.