8tablespoons(113 g or 1 stick) unsalted butter, softened but still cool
¾cupplus 2 tablespoons (175 g) granulated sugar
1large egg,, room temperature
¼teaspoonpure vanilla extract
⅛teaspoonlemon extract, or fresh-squeezed lemon juice
½cup(125 mL) whole milk, (2% works too)
Icing
¼cup(35 g) unsweetened chocolate, chopped fine
2tablespoons(40 g) light corn syrup
3tablespoons(44 mL) water
2 ½cups(300 g or 10 ounces) confectioners' sugar
¼teaspoonpure vanilla extract
Instructions
Cookies
Adjust the oven racks to the lower- and upper-middle positions and heat the oven to 375° F. Line 2 cookie sheets with parchment paper or spray with nonstick spray.
Whisk together the flour, baking powder, and salt in a large bowl; set aside. Using an electric mixer, beat the butter at medium speed until creamy, about 30 seconds. Gradually beat in the sugar, increasing the speed to medium high, until light and fluffy, about 3 minutes. Scrape down the sides and bottom of the bowl. Add the eggs, vanilla, and lemon extract and beat at medium speed until combined, about 30 seconds. Again, scrape down the sides and bottom of the bowl. Beginning and ending with the flour mixture, alternately add the flour mixture in 4 additions and the milk in 3 additions at low speed until just combined.
Using a 1/4-cup drying measuring cup, place six 1/4-cup-mounds of dough a generous 2-inches apart on each baking sheet. With moistened fingers, gently press each mound of dough into a disk 3-inches wide and 1/2-inch thick. Bake until the centers of the cookies are firm and the edges are just beginning to brown, about 20 minutes, rotating the baking sheets front to back and top to bottom halfway through the baking time. Cool the cookies on the baking sheets for 2 minutes. Using a wide metal spatula, transfer the cookies to a wire rack to cool completely. Repeat with the remaining dough.
Icing
Melt the chocolate in a medium bowl set over a saucepan of almost-simmering water (see tips for melting chocolate here). Remove form the heat and set aside. Bring the corn syrup and the water to a boil in a medium saucepan. Remove the pan from the heat and stir in the confectioners' sugar and vanilla until combined. Transfer 3/4 cup of the vanilla icing to the bowl with the melted chocolate and stir to combine.
Place 2 large wire racks on top of parchment paper or newspaper. Using a small offset metal spatula, spread about 2 tablespoons of the vanilla icing on half of each cookie. Tilt the cookie and run the spatula around the edge of the cookie to scrape off excess icing. Place the cookies on the wire rack and allow the icing to harden, about 15 minutes. Using the spatula, spread the chocolate icing on the other half of each cookie, tilting the cookie downward and scraping away excess icing. Place the cookies on the wire rack and allow the icings to harden, at least 1 hour.
Notes
Cookie dough consistency: The dough should be thinner than most cookie doughs. Somewhere between cake batter and cookie dough. It should not spread too much when you put the dough on prepared baking sheet. If it's too thin and spreads, add more flour one tablespoon at a time.Icing consistency: If the vanilla icing begins to thicken, stir in more hot water, teaspoon by teaspoon, until the icing is fluid enough to coat the cookies. Alternatively, if the icing is too thin and runny, whisk in additional confectioners' sugar, teaspoon by teaspoon. If the chocolate icing thickens and cools, reheat it over a pot of simmering water until it is fluid enough to coat the cookies. Storing black and white cookies: Place cookies between sheets of wax paper in an airtight container. Store at room temperature for 3 days or in the refrigerator for 5 days.Freezing black and white cookies: Place iced cookies on a baking sheet in the freezer for 1 hour to set. The wrap the cookie individually and store in an airtight container in the freezer for up to one month. You can also freeze un-iced cookies in an airtight container or bag for one month.Suggested tools:
Kitchen scale to measure and weigh ingredients accurately.
Hand mixer to combine the cookie dough ingredients.