01 - Beat softened butter and powdered sugar in a large bowl until smooth and fluffy. Incorporate vanilla extract until fully blended.
02 - Sift flour and salt into the butter mixture. Mix on low speed until just combined and dough begins to form. Avoid overmixing.
03 - Divide dough in half and form each portion into 2-inch diameter logs. Wrap tightly in plastic wrap and refrigerate for minimum 30 minutes until firm.
04 - Preheat oven to 350°F. Line baking sheets with parchment paper and set aside.
05 - Cut chilled dough logs into 1/2-inch thick rounds using a sharp knife. Place slices 2 inches apart on prepared baking sheets.
06 - Bake for 12 to 14 minutes until edges begin turning light golden. Remove from oven and let cool completely on baking sheets.
07 - Whisk egg yolks, granulated sugar, heavy cream, and vanilla in a small saucepan. Cook over medium-low heat, stirring constantly, for 4 to 5 minutes until slightly thickened. Remove from heat and allow to cool completely.
08 - Spread a small amount of cooled custard onto the center of each cooled cookie using a small offset spatula or spoon.
09 - Sprinkle a thin, even layer of granulated sugar over custard-topped cookies. Using a kitchen torch, caramelize sugar until golden brown and crispy. Let set for 5 minutes before serving.