1. Preheat oven to 350 degrees F. Line 2 baking sheets with parchment paper.
2. Prepare the cookies. In a medium bowl, combine flour, cornstarch, baking powder,baking soda, and salt. Set aside.
3. In a large bowl, use an electric mixer on medium speed to cream butter. Gradually add sugar, beating until the mixture is light and fluffy, about 5 minutes. Add the eggs 1 at a time, beating well after each addition, then beat in the vanilla and lemon zest. With the mixer set on low speed, add the flourmixture, alternating with the buttermilk, in 2 additions each (beginning with flour and ending with milk). Dough will be sticky.
4. Use a large spoon or ice cream scoop to drop 2 Tbsp. dough in mounds on theprepared baking sheets; there should be 24. Space them about 2 inches apart. Moisten your hands and gently press and flatten the dough mounds slightly with your palms; with your moistened fingertips, round off the dough to make neat circles. The cookies should be about 3 inches in diameter and about 1/2 inch thick.
5. Bake the cookies until the edges are pale brown, about 16 to 18 minutes. Let cookies cool on the pans for 2 to 3 minutes, then transfer to racks to cool completely.
6. Prepare the vanilla glaze. In a large bowl, combine the confectioners' sugar, milk, corn syrup, and vanilla. Stir until well combined and smooth.
7. When the cookies have cooled completely, spread one half of one side of each cookie with the vanilla glaze. Place the cookies, glazed side up, on racks or sheets of waxed paper and let them sit until the glaze is fully set, about 30 minutes.
8. Prepare the chocolate glaze. In a large bowl, stir together the confectioners' sugar and cocoa. Stir in the milk and corn syrup until smooth, then stir in the melted chocolate. Stir until well combined and smooth. Add additional milk if needed for a smooth, spreadable consistency.
9. When the vanilla glaze is set, spread the chocolate glaze on the other half next to the vanilla glaze (the surface should be half black and half white). Set the glazed cookies on racks or waxed paper until the chocolate glaze is set, about 40 minutes. Serve at room temperature. Store with waxed paper between layers in airtight containers.
Source: Hannaford fresh Magazine, July - August 2011