Heat 2 cups of whole milk in a saucepan over medium heat until steaming, but do not let it boil.

Whisk together 4 egg yolks, 1/2 cup granulated sugar, 1/4 teaspoon salt, 1 tablespoon vanilla bean paste, and 2 tablespoons cornstarch in a separate bowl until pale.

Gradually add the steaming milk to the egg mixture, stirring constantly.

Return to the saucepan and cook for 8-12 minutes until thickened.

Remove from heat and stir in 2 tablespoons of unsalted butter.

Let it cool.

Preheat your oven to 350°F (175°C).

In one bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking powder, and a pinch of salt.

In another bowl, cream together 1/2 cup unsalted butter and 3/4 cup granulated sugar until light and fluffy, about 3-4 minutes.

Incorporate 1 egg and another teaspoon of vanilla bean paste into the butter mixture.

Gradually blend in the dry ingredients until just combined.

Roll the cookie dough into 1-inch balls and roll each in granulated sugar to coat.

Arrange on lined baking sheets about 2 inches apart and gently flatten each ball.

Bake the cookies for 9-10 minutes, or until the edges are just starting to turn golden and centers remain soft.

Allow to cool on the sheet for about 5 minutes before transferring to a wire rack.

Pipe cooled pastry cream onto the center of each cookie.

Sprinkle a thin layer of granulated sugar over the pastry cream.

Caramelize the sugar with a kitchen torch until golden and bubbly.

Serve immediately for best texture.