Prepare Pastry Cream: Heat 2 cups of whole milk over medium heat until it starts steaming. In a bowl, whisk together 4 egg yolks, ½ cup granulated sugar, 1 tablespoon vanilla bean paste, a pinch of salt, and 2 tablespoons cornstarch. Gradually pour the hot milk into the egg mixture while whisking, then return to low heat and cook, stirring continuously, about 5-7 minutes until thickened. Stir in 2 tablespoons of unsalted butter and cover with plastic wrap to cool in the fridge.

Make Cookie Dough: Preheat oven to 350°F (175°C). Whisk together 2 cups all-purpose flour, 1 teaspoon baking powder, and a pinch of salt in one bowl. In another bowl, cream ½ cup unsalted butter and 1 cup granulated sugar until fluffy, about 3-5 minutes. Mix in 1 egg and 1 teaspoon of vanilla until combined. Gradually incorporate dry ingredients into the wet mixture until just combined.

Shape Cookies: Scoop tablespoon-sized portions and roll into balls. Roll in granulated sugar and flatten slightly with your palm. Arrange on parchment-lined sheets, leaving space for spreading.

Bake Cookies: Bake for 9-10 minutes until edges are lightly golden and centers are soft. Allow to cool on bake sheets for 5 minutes before transferring to wire racks.

Assemble Cookies: Take cooled pastry cream, transfer to a piping bag, and pipe onto cookie centers. Sprinkle granulated sugar on top for the brûlée finish.

Brûlée the Topping: Use a kitchen torch to caramelize sugar on top of each cookie until golden and bubbly. Allow to cool slightly.

Serve and Enjoy: Serve cookies immediately after assembling for the best texture and flavor.