Prepare the Puff Pastry:

Preheat the oven to 400°F (200°C).

Place the puff pastry sheets on a baking sheet lined with baking paper.

Prick the pastry sheets all over with a fork to prevent them from puffing too much.

Bake for 10-15 minutes or until golden and crisp.

Allow to cool on a cooling rack.

Prepare the Vanilla Custard Filling:

In a large saucepan, combine the milk, heavy cream, and half of the sugar.

Split the vanilla bean lengthwise, scrape out the seeds, and add both seeds and bean to the saucepan (or add the vanilla extract).

Heat the mixture over medium heat until it starts to simmer. Remove from heat and let it sit for 10 minutes to infuse the vanilla flavor.

In a medium mixing bowl, whisk together the remaining sugar, cornstarch, and egg yolks until smooth.

Gradually pour the warm milk mixture into the egg mixture, whisking constantly.

Return the mixture to the saucepan and cook over medium heat, whisking continuously, until it thickens and comes to a boil.

Remove from heat and stir in the butter until smooth.

Transfer the custard to a bowl, cover with plastic wrap (pressing it directly onto the surface to prevent a skin from forming), and let it cool to room temperature.

Assemble the Vanilla Slice:

Place one sheet of puff pastry in the bottom of a square baking dish.

Pour the cooled custard over the pastry, spreading it evenly.

Place the second sheet of puff pastry on top of the custard, pressing down gently.

Prepare the Vanilla Icing:

In a medium mixing bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth and spreadable.

Spread the icing over the top layer of puff pastry.

Chill and Serve:

Refrigerate the assembled vanilla slice for at least 2 hours to allow the custard to set.

Once set, use a sharp knife to cut the slice into squares.

Serve chilled and enjoy!

This Classic Vanilla Slice is a delightful and elegant dessert, perfect for any special occasion or simply to indulge your sweet tooth!