Preheat oven to 350 degrees F. Line a baking sheet with parchment paper.
In a mixer, cream butter and sugar together for a few minutes. Add egg then stir in the peppermint extract. Add flour, cocoa powder, baking soda, baking powder and salt. Mix until just well combined. Place dough balls on baking sheet.
Bake for about 10-11 minutes until the edges are golden brown. Remove from oven and allow them to cool completely.
While you’re waiting for the cookies to cool, make the chocolate frosting. In a mixer, add powdered sugar, cocoa powder, and butter. Mix well. Add whipping cream and vanilla extract. Mix until smooth.
Spread chocolate frosting on top of cooled cookies then garnish with crushed peppermint candies. Enjoy!