Vanilla Bean Sables

In the bowl of a stand mixer fitted with a paddle attachment, beat butter on medium until creamy, about 1 minute. Add granulated and powdered sugars, the salt and vanilla bean seeds or paste (if using); beat on medium until creamy and combined, 2 to 3 minutes. Add egg yolks and vanilla extract (if using); mix on low. Add flour; mix on low until combined.

Transfer dough to a lightly floured surface. Shape dough into a 12- to 13-inch log, then place it on a piece of plastic wrap a few inches longer than the log. Sprinkle turbinado sugar over log, covering it completely. Gently press sugar into dough with your hands, then wrap log tightly. Refrigerate until firm, about 2 hours or overnight.

Position an oven rack in the middle of the oven and preheat to 350°. Line three cookie sheets with parchment paper.

Unwrap chilled log and cut into slices just under 1/2 inch thick. Place slices 2 inches apart on prepared cookie sheets. Bake one pan at a time, rotating pan halfway through baking, until the edges are very light golden brown but the centers are still pale, 14 to 16 minutes. Let cookies cool completely on cookie sheets set on wire racks. Store in an airtight container at room temperature up to 3 days.