Preheat the oven to 350°F. Line a cookie sheet with parchment paper or a silicone baking sheet and set aside.

In the bowl of a stand mixer or with an electric hand mixer, cream together the butter and sugar. Mix for about 2 minutes, until the mixture is light and fluffy.

Scrape the sides of the bowl, add in the egg and vanilla. Mix well.

Next, add the flour, baking soda and salt to the bowl. Begin mixing and while the dry ingredients are being combined, slowly pour in the buttermilk. Mix until you have a smooth, thick batter.

Use a #24 cookie scoop to portion out the batter onto the prepared baking sheet. The cookies will spread so be sure to leave room for the cookies to expand.

Bake at 350°F for 12-14 minutes or until the cookies have flattened, spread and the center of the cookie bounces back if gently tapped on.

Allow the cookies to cool completely on the pan.

Once the cookies are cool, make the icing.

Make the icing by whisking together the warm water, corn syrup and clear vanilla in a medium sized bowl.

Slowly add the powdered sugar to the water mixture, whisking constantly and adding a few drops of more warm water as needed until all of the powdered sugar has been incorporated. Add warm water 1/4 tsp at a time until you reach a very slow dripping consistency.

Divide the icing in half.

You will leave one bowl as white vanilla icing. To the other half of the icing, add the cocoa powder, whisking and adding drops of water as needed until combined with that same slow, dripping consistency.

Ice the bottoms of the cookies, half white and half chocolate. I like to pipe a tiny line with the white icing down the center and then use an offset spatula to ice the white side first and then allow that to crust before using another offset spatula to ice the chocolate side. I generally ice all of the cookies with the white and then go in with the chocolate icing.

Allow the icing to harden and then serve! Store in an airtight container for up to 3 days. Enjoy!