Adapted from Joy the Baker
- 1 stick butter
- 1/4 cup (50 grams) granulated sugar
- 2 tablespoons (15 grams) powdered sugar
- 1/4 teaspoon salt
- 1 egg, separated
- 1 teaspoon vanilla extract
- 1 cup (130 grams) flour
- Turbinado sugar, for decorating
Working in a mixer fitted with a paddle attachment, beat the butter at medium speed until it is smooth and very creamy. Add the sugars and salt to the butter and continue to beat until smooth and velvety, not fluffy and airy, about 1 minute. Reduce the mixer speed to low and beat in the egg yolk until well blended.
Turn off the mixer, pour in the flour and mix on low speed just until the flour disappears into the dough and the dough looks uniformly moist. If you still have some flour on the bottom of the bowl, stop mixing and use a rubber spatula to work the rest of it into the dough. (The dough will not come together in a ball — and it shouldn’t. You want to work the dough as little as possible. What you’re aiming for is a soft, moist, clumpy dough. When pinched, it should feel a little like Play-Doh.)
Scrape the dough onto a work surface and gather it into a ball. Shape into a smooth log about 9 inches long (it’s easiest to work on a piece of plastic wrap and use the plastic to help form the log). Wrap the log well and chill for at least 2 hours. The dough may be kept in the refrigerator for up to 3 days or frozen for up to 2 months.
When ready to bake, center a rack in the oven and preheat the oven to 350 degrees. Line a baking sheet with a silicone baking mat or parchment paper and keep it at the ready.
To decorate the edges of the sables, whisk the egg white until smooth. Place chilled log of dough on a piece of waxed paper and brush it with the white, and then sprinkle the entire surface of the log with turbinado sugar. Trim the ends of the roll if they are ragged and slice the log into 1/3-inch-thick cookies (I got around 18 cookies). May chill the dough again at this point if desired, or proceed directly on to baking.
Place the rounds on the baking sheet, leaving an inch of space between each cookie, and bake for 17 to 20 minutes (mine went the whole 20), rotating the baking sheet at the halfway point. When properly baked, the cookies will be light brown on the bottom, lightly golden around the edges and pale on top. Let the cookies rest 1 or 2 minutes before carefully lifting them onto a cooling rack with a wide metal spatula. Repeat with the remaining log of dough.