01 - Beat softened butter and powdered sugar in a large bowl until smooth and fluffy, approximately 3 minutes. Incorporate vanilla extract until fully combined.
02 - Sift flour and salt into the butter mixture. Mix on low speed until just combined and dough begins to form, being careful not to overwork.
03 - Divide dough into two equal portions. Roll each into a 2-inch diameter log, wrap tightly in plastic wrap, and refrigerate for 30 minutes until firm.
04 - Set oven to 350°F and line baking sheets with parchment paper.
05 - Slice chilled dough logs into 1/2-inch thick rounds. Arrange on prepared baking sheets and bake for 12-14 minutes until edges are lightly golden. Cool completely on wire racks.
06 - Whisk together egg yolks, 1/4 cup granulated sugar, heavy cream, and vanilla in a small saucepan. Cook over medium-low heat, stirring continuously, until mixture thickens slightly, about 4-5 minutes. Remove from heat and cool completely.
07 - Spread a small amount of cooled custard onto the center of each cookie using a small offset spatula or spoon.
08 - Sprinkle a thin, even layer of granulated sugar over the custard topping. Using a kitchen torch, caramelize the sugar until golden brown and crispy. Allow to set for 5 minutes before serving.