Preheat the oven to 350 degrees. Prepare a large baking sheet with parchment paper.
In a medium bowl, whisk together the flour, cocoa, baking soda, and salt. Set aside.
Beat the butter and medium speed for 5 minutes. Scrape down the sides. Add the sugars and continue beating for 5 to 7 minutes or until fluffy.
Mix in the vanilla and eggs until combined.
Add the flour mixture and beat until mixed.
Using a small (1 tablespoon) cookie scoop, portion the cookie dough and shape into balls. Place on the baking sheet about 1 inch apart.
Roll the cookie dough balls into the crushed candy canes or sprinkles if desired. See notes about chilling the dough if you are using candy canes.
Bake for 8 to 10 minutes or until the cookies are puffed and the edges are set.
After removing the cookies from the oven, press one kiss into the center of each cookie.
Transfer to a wire rack and allow the cookies to cool completely. The candies will look like they are melting but do not disturb them and they will resolidify in the correct shape.
Store in an airtight container for up to 1 week or refrigerate for up to 3 weeks. Cooled cookies can also be frozen but sudden temperature changes may cause the candy to “bloom” which is harmless but not pretty.