In a large bowl, whisk together the flour, cocoa powder, baking soda and and salt. Set aside.
In a medium bowl, whisk together the egg, vanilla, food color, and milk. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium until pale and creamy. Add the sugars and continue beating until fluffy. Reduce the speed to medium low and add the egg mixture. Stir until combined, scraping down the sides as necessary. Reduce the speed to low and slowly add the flour mixture, just until combined, scraping down the sides as necessary.
Place a sheet of plastic wrap on the counter and transfer dough on top of the plastic. Cover with another sheet of plastic wrap and shape into a 12" log. Chill* in the refrigerator for at least 4 hours or overnight.
Pre-heat oven to 350°F and line a baking sheet with parchment paper or silpat. Remove the dough from the refrigerator slice the log into 1/4-inch thick discs**. Transfer to the prepared baking sheet, leaving 2-inches in between each disc. Bake for 11 - 12 minutes, just until the edges begin to crisp slightly. Allow to cool on the baking sheet.
Decorate cooled cookies with a green cream cheese frosting.*** Decorate or garnish with festive candy.
Cream Cheese Frosting
Using a stand mixer or a hand mixer, beat together the cream cheese and butter until smooth.
Add the vanilla and beat until combined. Slowly add the sugar and beat until smooth. Add the cream or milk a little at a time until desired consistency. Add the food coloring until desired color is reached. Cover and chill until ready to use.
Notes
*Chilling is mandatory.**If the discs become oblong, you can shape it into a perfect round or use the edge of a round glass to cut out perfect circles. If the dough becomes too soft to handle, return to the refrigerator to chill for 30 minutes before proceeding.***I transferred the frosting to a piping bag fitted with a small round tip. To create a pine needle effect, in one continuous motion, I piped a border around the edge of the cookie and every few centimeters would move the piping bag back slightly to overlap frosting onto the previously piped frosting.****Only use brick-style cream cheese