Make the Simple Crust: Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving a little overhang to easily lift the squares later.
In a medium bowl, combine the flour, 2 tablespoons of granulated sugar, and a pinch of salt. Add the cold, cubed butter and use your fingers or a pastry cutter to mix until it forms a crumbly, coarse meal.
Press this mixture firmly and evenly into the bottom of your prepared pan. Bake for 18-22 minutes, or until the edges are just lightly golden. Let the crust cool completely on a wire rack while you prepare the custard.
Whip up the Silky Custard: In a saucepan, whisk together the ½ cup of granulated sugar and cornstarch until there are no lumps. Gradually whisk in the whole milk and egg yolks until the mixture is smooth.
Place the saucepan over medium heat and stir constantly with a whisk or spatula. Keep stirring for about 5-7 minutes, until the custard thickens to a beautiful, creamy consistency. Remove the pan from the heat.
Stir in the 2 tablespoons of butter, vanilla extract, and a pinch of salt until everything is well combined and the custard is glossy.
Assemble & Chill to Perfection: Pour the warm, silky custard evenly over the completely cooled crust in your baking pan. Gently smooth the top with a spatula.
Refrigerate the pan for at least 1 hour (or longer if needed) until the custard is fully set and firm enough to slice neatly.
Serve a Delightful Treat: Once chilled, use the parchment paper overhang to carefully lift the entire slab of squares from the pan. Slice into individual squares.
For an optional elegant touch, dust lightly with powdered sugar before serving. These squares are best enjoyed chilled!