A New York specialty for more than half a century, these cookies taste best the day after they are made. Wrap in plastic and keep overnight at room temperature.

　　

Ingredients

makes about 18

　　3 cups all-purpose flour

　　1/4 teaspoon baking powder

　　1/4 teaspoon baking soda

　　1/4 teaspoon salt

　　1 1/4 sticks (10 tablespoons) unsalted

　　butter, room temperature

　　1/2 cup vegetable shortening

　　1 cup plus 3 tablespoons sugar

　　2 large whole eggs, plus 1 large egg yolk

　　1 tablespoon pure vanilla extract

　　1/4 cup heavy cream

　　Black and White Icings (recipe follows)

　　

Black and White Icings

1 cup heavy cream

　　3 1/2 cups confectioners’ sugar, sifted

　　5 tablespoons Dutch-process cocoa powder

　　6 tablespoons boiling water

　　(makes enough for about 18 cookies)

　　

Step 1

Preheat the oven to 350°F. Line two large baking sheets with parchment paper; set aside. In a bowl, whisk together the flour, baking powder, baking soda, and salt. In the bowl of an electric mixer fitted with the paddle attachment, beat the butter, shortening, and sugar on medium speed until light and fluffy, about 3 minutes, scraping down the sides of the bowl as needed. Add whole eggs and egg yolk, one at a time; beat until combined after each addition. Beat in vanilla. Add the flour mixture in two batches, alternating with the cream. Beat until just combined (do not overmix).

　　

Step 2

Use a 1/4-cup measure to scoop dough 3 inches apart onto prepared sheets. Bake, rotating sheets halfway through, until the edges just begin to turn golden and the centers are cakey and tender, 10 to 12 minutes. Transfer parchment and cookies to a wire rack to cool for 10 minutes. Remove cookies from parchment and let cool completely.

　　

Step 3

On the flat side (bottom) of each cookie, use a small offset spatula to spread chocolate icing over one half of the cookie, creating a line straight down the center. Spread white frosting on the other half. Set cookies aside until icing is set, about 30 minutes.

　　

Black and White Icings

Step 4

Whisk cream into sugar until smooth. Set aside 1 1/4 cups (for white icing).

　　

Step 5

Combine cocoa with boiling water, and stir until dissolved. Add to remaining sugar mixture; stir to combine (for black icing). Use immediately.

　　

Black and White Cookie how-to

Step 6

One half of the flat side of each cookie is carefully covered with chocolate icing using a small offset spatula; white icing is spread on the other half.

　　Reprinted with permission from Martha Stewart's Baking Handbook by Martha Stewart. © 2005 Clarkson Potter