1) Sift dry ingredients (flour, cocoa powder, baking soda, salt) into a large bowl.
2) Add butter and sugar to a mixing bowl and cream them together.
3) Mix in vanilla and eggs.
4) Slowly add in flour and buttermilk in alternating stages to creamed butter. Start with dry ingredients and end with dry ingredients. It goes 1/3 of flour, 1/2 of buttermilk, 1/3 of flour, 1/2 of buttermilk, and finally the last 1/3 of flour.
5) Mix it together on low until it all is combined.
6) Spoon dollops of it onto a parchment paper lined baking sheet.
7) Bake at 350 degrees for 11-13 minutes. Rotate pans once to make sure they cook evenly. They should be slightly springy when they are done.
8) Let cool on the sheet for a minute or two and then move them to a wire rack to cool. Let them cool completely.
9) For filling, add room temperature butter to mixer and mix on medium until it is creamy.
10) Add in tiny amount of peppermint.
11) Once flavoring is added, slowly add in sifted confectioners sugar.
12) Once all sugar is incorporated, add drops of food coloring.
13) Slather on as much of the mixture as you want between two of your baked cookie-cake things. Repeat!