Vanilla Custard Cream Squares

Preheat oven to 400°F (200°C).
Line two baking sheets with parchment paper.
Place each puff pastry sheet on a baking sheet. Prick all over with a fork to prevent puffing too much.
Brush lightly with beaten egg.
Place another sheet of parchment on top and a second baking tray to weigh it down (this keeps layers even).
Bake for 15–20 minutes, or until golden brown and crisp.
Let cool completely, then trim edges to make even rectangles that fit into your pan (an 8×8 or 9×9 inch square pan works well).

In a medium saucepan, heat 2½ cups milk over medium heat until steaming (not boiling).
In a separate bowl, whisk together sugar, cornstarch, salt, egg yolks, and remaining ½ cup milk until smooth.
Slowly pour the hot milk into the yolk mixture while whisking constantly.
Return mixture to the saucepan and cook over medium heat, stirring constantly, until thick and bubbling (about 4–6 minutes).
Remove from heat and stir in butter and vanilla extract.
Pour the custard into a bowl, cover surface directly with plastic wrap, and let it cool to room temperature.

Mix powdered sugar, vanilla, and enough milk/water to make a smooth, pourable icing.
Spread over the top pastry layer.
For a marbled effect, drizzle thin lines of melted chocolate and drag a toothpick through.
Chill another 30 minutes to set.
Cut into squares using a sharp knife (dip in hot water for cleaner slices).

For a lighter version, fold some whipped cream into the cooled custard before assembling.
You can also use store-bought vanilla pudding in a pinch, though homemade custard gives the best flavor.
Keeps in the fridge for up to 3 days — best served cold.