01 - Beat unsalted butter and powdered sugar in large bowl until smooth and fluffy. Incorporate vanilla extract until fully combined.
02 - Sift flour and salt into butter mixture. Mix until just combined and dough begins to form. Do not overmix.
03 - Divide dough in half and shape into 2-inch diameter logs. Wrap tightly in plastic wrap and refrigerate for minimum 30 minutes.
04 - Preheat oven to 350°F. Line baking sheets with parchment paper.
05 - Cut chilled dough logs into 1/2-inch thick rounds. Place cookies 2 inches apart on prepared baking sheets.
06 - Bake for 12 to 14 minutes until edges are lightly golden. Remove from oven and let cool completely on baking sheets.
07 - Whisk egg yolks, sugar, heavy cream, and vanilla in small saucepan. Cook over medium-low heat, stirring constantly, until mixture thickens slightly, 4 to 5 minutes. Remove from heat and cool completely.
08 - Spoon small amount of cooled custard onto center of each cookie. Gently spread to create even layer.
09 - Sprinkle thin layer of granulated sugar over custard topping. Use kitchen torch to caramelize until golden and crisp. Let set 5 minutes before serving.