01 - Beat the unsalted butter and powdered sugar together in a large bowl until the mixture is smooth and fluffy. Stir in the vanilla extract until fully incorporated.
02 - Sift the all-purpose flour and salt into the butter mixture. Mix until just combined and a cohesive dough forms, taking care not to overwork.
03 - Divide the dough in half and shape each portion into logs approximately 2 inches in diameter. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes until firm.
04 - Set oven temperature to 350°F and line baking sheets with parchment paper.
05 - Cut the chilled dough logs into 1/2-inch thick rounds. Place the rounds on the prepared baking sheets, spacing them evenly.
06 - Bake for 12 to 14 minutes or until the edges begin to turn golden brown. Remove from oven and allow to cool completely on the baking sheets.
07 - Whisk together the 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 let cool completely.
08 - Spoon a small amount of the 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. Use a kitchen torch to caramelize the sugar until golden and crisp. Allow the caramelized layer to set for 5 minutes before serving.