By Carol Ramos, The Pastry Chef's Baking
Adapted from "Great Cookies" by Carole Walter
3 cups all-purpose flour, spooned in and leveled
1/2 teaspoon salt
1/4 teaspoon baking soda
1/4 teaspoon cream of tartar
1 cup (2 sticks) unsalted butter, slightly firm, cut into 1-inch pieces
1-1/4 cups superfine sugar
2 large eggs, separated
2 teaspoons pure vanilla extract
2 tablespoons milk
2 teaspoons water
1/3 cup sparkling white sugar, for garnish
1. Preheat the oven to 375 degrees F. Line the cookie sheets with parchment paper.
2. Whisk together the flour, salt, baking soda, and cream of tartar. Set aside.
3. In the large bowl of an electric mixer fitted with the paddle attachment, beat the butter on medium speed until smooth and lightened in color, 1-1/2 to 2 minutes. Add the sugar 1/4 cup at a time and beat for 2 minutes longer. Add the egg yolks and vanilla, mixing for 1 minute longer. Scrape down the bowl as needed.
4. On low speed, add half of the dry ingredients, then add the milk, and then the remaining dry ingredients, mixing only to combine.
5. With lightly floured hands, shape about 1/4 cup of the dough into a ball. Place six balls of dough about 3 inches apart on each cookie sheet. Using the heel of your hand, press each ball into a 3- to 3-1/2-inch disk. Using a flat-bottomed glass lightly dipped in flour, flatten each disk into a 4-inch circle.
6. Combine the egg whites with the water and beat lightly with a fork. Brush the top of each disk heavily with the egg wash (or omit completely if you prefer). Sprinkle with 1/2 to 3/4 teaspoon of sparkling white sugar. Bake the cookies for 13 to 14 minutes, or until the edges are lightly browned. Let rest on the cookie sheets for 3-5 minutes, or until firm enough to handle. Transfer the cookies to a wire rack and let cool completely.
7. Store in an airtight container, layered between strips of wax paper, for up to 3 weeks. These cookies may be frozen. (My recommendation is freeze the cookie dough and bake the cookies when you need them so they'll always be fresh.)