Answer:
Preheat oven to 350°F.
Sift together flour, baking soda and salt in medium bowl.
In small bowl or cup, mix together buttermilk and vanilla.
Beat butter and white sugar together in a large mixing bowl with an electric mixer for about 3 minutes or until it's evenly distributed.
Add egg to butter and sugar mixture, and beat until blended.
Gradually beat in flour mixture one cup at a time, and add in buttermilk mixture between each cup of flour, and mix until smooth. It will be necessary to scrape down the sides of the bowl while mixing.
Spoon batter in 1/4 cup size servings onto a baking sheet lined with parchment paper.
Bake on middle rack for about 15-17 minutes, or until the tops are golden brown and spring back when touched.
Place on a cooling rack, and allow to cool completely before icing.
Stir together icing sugar, corn syrup, lemon juice, vanilla, and 1/2 Tbsp of water in bowl until smooth.
Place half of mixture into separate bowl and add cocoa powder, and remaining water bit by bit until it is the same consistency as the white icing. If the icing is too runny, add more icing sugar until it is smooth and spreadable.
Turn cooled cookies flat side up, and spread icing with pastry spatula, or butter knife. White over one half, chocolate over the other. The icing does not set solid on these cookies, and does not harden, but it dries enough to be wrapped as they are sold in the city. They can be wrapped individually in cellophane, or sealed in a plastic container
Explanation: hope this helps!