Black and White Cookies
Makes about 24 large cookies

Note: Don’t substitute “lemon flavor” or lemon oil for the lemon extract. However, in a pinch you can substitute fresh lemon juice. If the chocolate icing cools so that it is no longer spreadable, microwave it for 30 seconds to soften.
COOKIES
4 cups (1 pound) cake flour ½ teaspoon baking powder ½ teaspoon salt 1 cup unsalted butter (2 sticks), softened 1¾ cups (12¼ ounces) sugar 2 large eggs, room temperature 1 teaspoon vanilla extract ½ teaspoon lemon extract 1 cup whole milk  ICINGS
¼ cup light corn syrup
⅓ cup water
5 cups (20 ounces) confectioners’ sugar
½ teaspoon vanilla extract
2 ounces unsweetened chocolate, melted
2–4 teaspoons water
FOR THE COOKIES: Adjust oven racks to upper-middle and lower-middle positions and heat oven to 350 degrees. Line 2 large baking sheets with parchment paper. Whisk flour, baking powder, and salt together in medium bowl.
Using stand mixer fitted with paddle, beat butter and sugar together on medium speed until light and fluffy, 3 to 6 minutes. Add eggs, vanilla, and lemon extract to bowl and continue to beat until combined, about 30 seconds, scraping down bowl and beaters as needed.
Reduce mixer speed to low and beat in one-third of flour mixture, followed by half of milk. Repeat with half of remaining flour mixture and remaining milk. Beat in remaining flour mixture until combined.
Scoop ¼-cup mounds of batter onto prepared sheets, spaced about 2 inches apart. Use back of spoon or finger dipped in water to smooth tops of cookies. Bake cookies until edges are just beginning to turn light golden brown, about 15 minutes, switching and rotating sheets halfway through baking. 
Let cookies cool on sheets for 10 minutes, then transfer to wire rack and let cool completely, about 1 hour. Repeat with remaining dough, using cooled, freshly lined sheets

FOR THE ICINGS: Bring corn syrup and water to boil in medium saucepan over medium-high heat. Off heat, whisk in confectioners’ sugar and vanilla until smooth. Measure half of icing into separate bowl and whisk in melted chocolate and 2 to 4 teaspoons water as needed until mixture is smooth and spreadable.
Place 2 large wire racks over parchment paper (for easy cleanup). Spread about 2 tablespoons chocolate icing over half of each cookie with small spatula, then let sit on wire racks until icing has just set, about 15 minutes. Spread vanilla icing over other half of each cookie and let sit until icings have hardened, about 1 hour, before serving.

 

Recipe from Test Kitchen