Step 1: Prepare the Pastry

In a large bowl, mix the flour, sugar, and salt.

Add cold cubed butter to the mixture. Use your fingertips or a pastry cutter to mix until the texture resembles coarse crumbs.

Add the egg yolk and blend it into the dough. Gradually add ice water, one tablespoon at a time, until the dough forms. You may not need all the water.

Shape the dough into a disc, wrap it in plastic wrap, and refrigerate for 30 minutes.

Step 2: Roll Out the Pastry

After chilling, lightly flour your countertop and rolling pin.

Roll out the dough into a rectangle (10×8 inches). Transfer it to a greased or parchment-lined baking pan.

Prick the dough with a fork to prevent puffing. Bake at 375°F (190°C) for 15-18 minutes until golden. Set aside to cool.

Step 3: Make the Custard Cream

Heat milk over medium heat in a saucepan until it’s almost boiling, stirring occasionally.

Whisk together egg yolks, sugar, and cornstarch in a separate bowl until smooth.

Gradually pour half of the hot milk into the egg mixture, whisking constantly. Return the mixture to the saucepan with the remaining milk and cook, whisking, until thickened (5-7 minutes).

Remove from heat and stir in vanilla extract and butter until smooth. Allow it to cool for a few minutes before pouring it over the cooled pastry crust.

Step 4: Assemble the Squares

Pour the custard over the cooled pastry and spread it evenly.

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

Step 5: Cut and Serve

After the custard has set, cut the dessert into squares or rectangles.

Dust the top with powdered sugar before serving.