Cream unsalted butter with granulated sugar and brown sugar until light and fluffy, about 3-4 minutes. Beat in eggs one at a time, followed by vanilla bean paste.

In a separate bowl, whisk flour, baking powder, and salt, then gradually add to the creamed mixture until a soft dough forms.

Cover dough with plastic wrap and refrigerate for at least 30 minutes.

Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper and scoop dough onto it. Bake for 9-12 minutes until edges are golden.

Heat milk in a saucepan. Mix together sugar, egg yolks, and cornstarch in a bowl, then slowly add hot milk. Return to saucepan and cook until thickened.

Once cookies are cooled, pipe or spoon pastry cream into the center of each cookie.

Sprinkle granulated sugar on filled cookies and using a kitchen torch, caramelize until golden brown.