Preheat oven to 350°F.
In medium bowl, stir together cookie mix, butter and egg until well blended.
Place rounded tablespoons dough 2-inches apart onto parchment lined cookie sheet. Bake 11-13 minutes.
Cool cookies completely.
To make chocolate buttercream frosting: With an electric mixer, beat butter and shortening until smooth. Add in melted chocolate chips and cocoa powder, mixing until smooth. Alternating mixing in powdered sugar and milk until you’ve reached your desired consistency. Add in vanilla and mix once more.
Spread 1-2 tablespoons of chocolate buttercream over each cookie. Arrange candy decorations to make a cat- candy corns for the eyes, chocolate chips for the ears, round chocolate candy for the nose and pull-apart licorice ropes for the whiskers.
Store cookies in an airtight container.