Preheat the oven to 350. For the chocolate flavor, add the butter and sugar to a bowl and mix for 2 minutes. Add egg and mix until just combined.
In a separate bowl, mix the buttermilk and vanilla. In another separate bowl, combine all the dry ingredients. Add half of the buttermilk to the butter/sugar mixture, and mix. Then add half of the dry ingredients and mix. Repeat with the remaining buttermilk and dry ingredients. Mix until just combined.
Scoop 2 tbsp of the dough onto a lined baking sheet and repeat. Up to 6 dough balls fit on one baking sheet. Bake at 350 for 10-13 minutes.
For the vanilla flavor, the process is the same!
To make the frosting, combine the butter and cream cheese and mix for 2 minutes. Add vanilla and powdered sugar and mix for an additional 2 minutes.
Separate the frosting into 3 bowls and add the food coloring. Put a large piece of plastic wrap on the counter and scoop the frosting onto the plastic wrap in long rows. Roll up the plastic wrap into a log. Twist the ends of the plastic wrap and cut one of the ends off. Transfer the log into a piping bag and pipe the frosting onto the cookies! Pipe onto one color, then top it with the other color. Enjoy!