Add the flour, powdered sugar, salt, and cold cubed butter to the bowl of a food processor.
Pulse the mixture until it resembles fine sandy crumbs. Be careful not to over-process. You're looking for a sandy texture with small butter pieces still visible.
Add the egg yolks and pulse until the dough begins to clump together into a soft dough. It will start off very crumbly but will eventually come together.
Divide the dough in two and place each half on a piece of parchment paper.
Roll each piece into a log about 2 inches (5 cm) in diameter. Wrap each log tightly in the parchment paper.
Refrigerate the dough logs for at least 2 hours or overnight. This step firms up the butter and makes the dough easier to slice cleanly.
Preheat your oven to 325°F (160°C) and line a baking sheet with parchment paper.
Unwrap the chilled logs. Spread a few tablespoons of turbinado sugar on a piece of parchment paper and roll each log in the sugar, pressing gently so it sticks all around.
Using a sharp knife, slice the logs into rounds about 1/3 to 1/2 inch (1 cm) thick.
Arrange the cookies on the prepared baking sheet, spacing them about 1 inch (2.5 cm) apart.
Bake for 16 to 20 minutes, or until the edges are just starting to turn golden. The lower temperature allows the cookies to bake gently, reducing the risk of browning too quickly on the edges before the center is done. Keep an eye on them, as oven temperatures vary and the thickness of your cookies will affect timing.
Allow the cookies to cool on the baking sheet for a few minutes to set, then transfer to a wire rack to cool completely.