Preheat the oven to 350° F.

In the bowl of a stand mixer fitted with a paddle, mix the butter and sugar on high speed until pale and creamy.

Add in the eggs one at a time, then the vanilla until incorporated.

In a separate bowl, combine the flour, cocoa powder, baking soda and salt.

Add to the butter mixture all at once and mix until incorporated. Be careful not to over mix.

Line a baking sheet with parchment paper.

Scoop out the dough into tablespoon sized portions and place onto the lined baking sheet.

Bake until surface is cracked and edges are dry. In my oven, this was about 10 minutes. 

Let cookies cool completely before icing.

My cookies did not flatten out as much as I would have liked in the oven.  To correct this, I used a spatula to flatten them and it turned out perfectly.

Using a stand mixer or a hand mixer and a large bowl, beat together the butter and the powdered sugar at slow speed.

Add the cream, peppermint extract and pinch of salt.

Mix at a low speed, until well combined.  

Increase speed and beat until smooth and whipped.  Approximately 2 to 3 minute.

As an option, you could add some food coloring to your icing to make it more festive.

Before moving onto the next step, make sure the cookies are cooled.  

Scoop the frosting into a piping bag with a large tip.

Frost one side of the cookie sandwich.

I decided to roll the cookie in various sprinkles to make it a bit more festive , but that's completely optional.