Begin by creaming the butter with granulated sugar until light and fluffy. Mix in the egg and vanilla extract. Gradually add flour until just incorporated.

Roll cookie dough into small balls and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C) while the dough chills. Bake cookie balls for 12-15 minutes until edges are light golden brown.

To create the vanilla pastry cream, heat heavy cream until warm. Whisk together egg yolks, granulated sugar, and cornstarch until smooth. Gradually combine with warm cream.

Cook mixture over medium heat, stirring constantly until thickened. Remove from heat and stir in vanilla extract. Allow to cool.

Fill the center of each cooled cookie with the pastry cream.

Sprinkle granulated sugar over the pastry cream and caramelize using a kitchen torch or broil in the oven.