Prepare the Pastry:

• Preheat your oven to 375°F (190°C).

• In a food processor, combine the flour, sugar, and salt. Add the chilled butter and pulse until the mixture resembles coarse crumbs.

• Gradually add the cold water and pulse until the dough comes together. Turn it out onto a floured surface and knead it gently until smooth.

• Roll out the dough into a rectangle large enough to fit a baking dish. Place it in a greased 9×13-inch baking dish, pressing it evenly across the base. Bake for 15 minutes or until lightly golden. Set aside to cool.

Make the Custard:

• In a medium saucepan, heat the milk over medium heat until it’s almost boiling. In a bowl, whisk together the egg yolks, sugar, and cornstarch until smooth.

• Gradually pour the hot milk into the egg mixture, whisking constantly to avoid curdling.

• Return the mixture to the saucepan and cook over medium heat, stirring constantly, until it thickens (about 5 minutes).

• Remove from heat and stir in the vanilla extract and butter. Let the custard cool for a few minutes.

Assemble the Squares:

• Once the pastry has cooled, spread the vanilla custard evenly on top. You can add another layer of pastry on top if desired, or leave it open for a creamier finish.

• Chill the dessert in the fridge for at least 2 hours to allow the custard to set.

Serve:

• Once set, cut the dessert into squares. Dust with powdered sugar before serving if desired.