01 - Cream together butter and powdered sugar in a large bowl until smooth and fluffy. Beat in vanilla extract until fully incorporated.
02 - Sift flour and salt into the butter mixture. Mix until just combined and a cohesive dough forms, being careful not to overwork.
03 - Divide dough in half and shape each portion into 2-inch diameter logs. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes until firm.
04 - Preheat oven to 350°F and line baking sheets with parchment paper.
05 - Slice chilled dough logs into 1/2-inch thick rounds. Place cookies on prepared baking sheets, spacing 1 inch apart.
06 - Bake for 12 to 14 minutes until edges just begin turning golden. Remove from oven and let cool completely on baking sheets.
07 - Whisk together egg yolks, 1/4 cup 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 - Spoon a small amount of cooled custard onto the center of each cooled cookie. Gently spread to create an even layer.
09 - Sprinkle a thin, even layer of granulated sugar over the custard topping. Using a kitchen torch, caramelize the sugar until golden and crisp. Let set for 5 minutes before serving.