Preheat your oven to 350°F (175°C) and line a 9x9 inch baking dish with parchment paper to avoid sticking.
Prepare the crust: Combine the graham cracker crumbs, melted butter, and granulated sugar in a bowl. Press this mixture evenly into the prepared baking dish and bake for 10 minutes until it just sets. Allow it to cool completely.
Start the custard: In a saucepan, gently warm the milk and heavy cream over medium heat. Concurrently, whisk together the sugar, egg yolks, vanilla extract, and cornstarch until smooth.
Slowly mix the egg mixture into the warmed milk, stirring constantly. Cook over medium heat, stirring until the custard thickens, approximately 5-7 minutes. You’ll know you’re done when it coats the back of a spoon. Let it cool slightly.
Assemble: Pour the custard over the prepared crust. Chill this in the refrigerator for a minimum of 2 hours, allowing it to set.
Whip the cream: Beat the heavy cream, powdered sugar, and vanilla extract to firm peaks. Spread this delicious whipped layer over the custard.
Finish and Serve: Chill once more, cut into squares, and serve. Revel in your handiwork!