For cookies:
1 1/4 cups all-purpose flour
1/2 tsp. baking soda
1/2 tsp. salt
1/3 cup well-shaken buttermilk
1/2 tsp. vanilla
1/3 cup (5 1/3 tbsp.) unsalted butter, softened
1/2 cup granulated sugar
1 large egg
For icings:
1 1/2 cups confectioners sugar
1 tbsp. light corn syrup
2 tsp. fresh lemon juice
1/4 tsp. vanilla
1 to 2 tbsp. water
1/4 cup unsweetened Dutch-process cocoa powder

Black & White Cookies

1. Preheat oven to 350° F. Whisk together flour, baking soda, and salt in a bowl. Stir together buttermilk and vanilla in a cup.
2. Beat together butter and sugar in a large bowl with an electric mixer until pale and fluffy, for about 3 minutes, then add egg, beating until combined well. Mix in flour mixture and buttermilk mixture alternately in batches at low speed (scraping down side of bowl occasionally), beginning and ending with flour mixture. Mix until smooth.
3. Spoon 1/4 cups of batter about 2 inches apart onto a buttered large baking sheet. Bake in middle of oven until tops are puffed and pale golden, and cookies spring back when touched, for 15 to 17 minutes. Transfer with a metal spatula to a rack and chill (to cool quickly), about 5 minutes.
4. Make icings while cookies chill. Stir together confectioners sugar, corn syrup, lemon juice, vanilla, and 1 tbsp. water in a small bowl until smooth. Transfer half of icing to another bowl and stir in cocoa, adding more water, 1/2 tsp. at a time, to thin to same consistency as white icing.
5. Ice cookies by turning cookies flat sides up, then spread white icing over half of each and chocolate over other half.
   Makes about 8 cookies
   Preparation time: 45 minutes