From The Gourmet Cookie Book, 2010 Conde Nast Publications
1 ¼ cups all-purpose flour
½ teaspoon baking soda
½ teaspoon salt
1/3 cup well shaken buttermilk
½ teaspoon vanilla
7 Tablespoons unsalted butter, softened
½ cup granulated sugar
1 large egg
2 ¾ cups powdered sugar
2 Tablespoons light corn syrup
2 teaspoons lemon juice (NOTE: if you don’t like your icing to be too lemony omit the juice and replace with water)
½ teaspoon vanilla
4-6 tablespoons water (or 6-8 if you've omitted lemon juice)
¼ cup unsweetened Dutch-process cocoa (I used Droste)
Put oven racks in upper and lower thirds of oven and preheat oven to 350. Line 2 cookie sheets with parchment paper and set aside.
Whisk together flour, baking soda and salt in a bowl.
Stir together buttermilk and vanilla in a cup.
Beat together butter and sugar in a large bowl with an electric mixer on medium-high until pale and fluffy, about 3 minutes.
Add egg and beat until thoroughly combined.
Reduce speed to low and add flour mixture and buttermilk mixture alternately in batches, beginning and ending with flour mixture. Mix just until smooth.
Depending on your desired cookie size use either a teaspoon (for really mini), 2 teaspoon sized scoop (for 2-inch cookies) or tablespoon (for 3-inch cookies) and drop batter onto cookie sheets, about 1 inch apart.
Bake, switching positions of sheets halfway through baking, until tops are puffy, edges are pale golden and cookies spring back to light touch, about 6-9 minutes depending on size. Transfer to wire rack to cool.
Site together powdered sugar, corn syrup, lemon juice, vanilla and 2 Tablespoons water in a medium bowl until smooth. If icing isn’t spreadable add more water a ½ teaspoon at a time.
Transfer half of the icing to another bowl and stir in the cocoa. The icing will become very stiff so add water, ½ teaspoon at a time (I need 3 teaspoons, just FYI) until the chocolate icing is the same consistency as the vanilla.
You will be frosting the cookies with the vanilla first so place a damp paper towel on the surface of the chocolate and wrap that bowl in plastic until ready to use.
Using a small offset spatula spread white icing over ½ of the flat bottom of the cookies.
Then starting with the cookies you iced first, complete the job by icing the other half with the chocolate icing. Place on rack and allow to set.
Yield: 60 mini OR 30 small OR 20 medium