01 - Cream butter and powdered sugar in large bowl until smooth and fluffy. Beat in vanilla extract until fully incorporated.
02 - Sift flour and salt into butter mixture. Mix until just combined and dough begins to form. Avoid overmixing.
03 - Divide dough in half and shape into 2-inch diameter logs. Wrap tightly in plastic wrap and refrigerate for minimum 30 minutes until firm.
04 - Set oven to 350°F and line baking sheets with parchment paper.
05 - Cut chilled dough logs into 1/2-inch thick rounds. Arrange on prepared baking sheets and bake for 12-14 minutes until edges turn lightly golden.
06 - Transfer cookies to wire rack and let cool completely before adding filling.
07 - Whisk egg yolks, granulated sugar, heavy cream, and vanilla in small saucepan. Cook over medium-low heat, stirring constantly, for 4-5 minutes until mixture thickens slightly. Remove from heat and let cool.
08 - Spoon small amount of cooled custard onto center of each cookie. Spread gently with offset spatula.
09 - Sprinkle thin layer of granulated sugar over custard filling. Torch sugar until golden brown and crisp. Let set 5 minutes before serving.