Make the Pastry Base: In a large mixing bowl, combine all-purpose flour, sugar, and salt. Mix with a fork. Add cold, cubed butter and work it into the flour to form pea-sized chunks. Add ice-cold water one tablespoon at a time until the dough starts to come together. Press into a disc, wrap in plastic wrap, and refrigerate for 30 minutes.

Roll out the dough on a floured surface to 1/4 inch thickness. Fit into a 9-inch tart pan, trim excess dough, and prick the bottom with a fork. Pre-bake at 375°F for 12-15 minutes until lightly golden.

In a medium bowl, whisk eggs until uniform. In a small bowl, mix cornstarch with 2 tablespoons of milk until dissolved. In a saucepan, combine heavy cream, remaining milk, and sugar. Warm over medium-low heat, stirring until sugar is dissolved.

Slowly pour the warm cream mixture into the whisked eggs while whisking constantly. Add the cornstarch mixture and vanilla extract. Pour through a fine mesh strainer into a bowl.

Pour the custard into the pre-baked pastry shell, leaving a small gap at the top. Bake at 325°F for 25-30 minutes until edges are set but the center has a slight wobble.

Evenly sprinkle granulated sugar over the chilled custard. Either torch the sugar until melted and caramelized or broil under the oven's broiler for 2-3 minutes until golden. Let cool briefly to harden.

Slice into 8 portions and serve with optional garnishes like fresh berries, powdered sugar, or mint leaves. Best served slightly chilled.