Chocolate Sables | America's Test Kitchen

Ingredients

• 1 large egg
• 10 tablespoons (1 1/4 sticks) unsalted butter , softened
• 1/3 cup plus 1 tablespoon granulated sugar (2 3/4 ounces/78 grams)
• 1/4 teaspoon table salt
• 1 teaspoon vanilla extract
• 1 1/3 cups unbleached all-purpose flour (6 2/3 ounces/189 grams)
• 1/4 cup Dutch-processed cocoa (1 ounce/28 grams)
• 1 teaspoon large egg white , lightly beaten with 1 teaspoon water
• 4 teaspoons turbinado sugar