While the cookies cool, prepare the icing.
Begin by whisking the confectioner’s sugar, corn syrup, lemon juice, vanilla, salt, and water together until smooth.
Separate the mixture into 2 bowls. Take one of the bowls of icing and add in the espresso powder and cocoa powder, whisking until smooth.
Feel free to add a few drops of water to the chocolate icing until it is a spreadable consistency. For me I had to add probably a tablespoon of water, in total, maybe more, to get the icing the right consistency.
The icing should be thin enough that it spreads easily, but not so thin that it is runny. If the icing seems to thick or dry, just add more water a half teaspoon at a time. If you add too much water, no problem, just add more confectioner's sugar 1 tablespoon at a time.
Once the cookies are completely cooled, flip them over so the flat sides are up.
Use an offset spatula or knife to spread vanilla icing on half of the cookies. Clean the spatula, and then spread the chocolate icing on the other half.
Once done, let the icing set for a few minutes, this is when I just stared at them because they looked so good. Once the icing is set, dig in!
Leftovers (if there are any) can be kept in an airtight container at room temperature for up to two days.