In a mixing bowl, combine the graham cracker crumbs, melted butter, and sugar. Stir everything together until the texture looks like damp sand and holds together when pressed.

Transfer this mixture into the prepared pan. Press it down firmly and evenly to form the base crust. Bake it for about 8–10 minutes, then take it out and allow it to cool completely.

While the crust cools, start the custard. In a saucepan, mix together the sugar, cornstarch, and salt first so there are no lumps later.

Gradually pour in the milk while whisking continuously until the mixture becomes smooth and well blended.

Place the saucepan over medium heat and keep stirring without stopping. After a few minutes, the mixture will start to thicken into a creamy custard.

In a separate small bowl, lightly whisk the egg yolks. To avoid scrambling them, slowly add a little of the hot mixture into the yolks while whisking. Then pour the tempered yolks back into the saucepan.

Continue cooking for another 2–3 minutes, stirring constantly until thick and silky. Remove from heat and mix in the butter and vanilla extract until the custard becomes smooth and glossy.

Pour the warm custard over the cooled crust and spread it evenly. Refrigerate for at least 4 hours, or until fully set and firm.

For the topping, whip the cream with powdered sugar and vanilla extract until soft peaks form. Spread it gently over the chilled custard layer, then cut into neat squares and serve.