In a large bowl with an electric mixer, or in the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium speed until blended.

Add the sugars and cream everything together until light and fluffy. Beat in the egg and vanilla, scraping down the sides of the bowl as necessary.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Slowly add to the wet ingredients while mixing on low speed. Add the milk and beat on medium speed until combined. Fold in chopped Candy Cane Hershey's Kisses. Dough will be thick and very sticky. Chill for at least 2 hours.

Preheat oven to 350ºF degrees. Line two large baking sheets with parchment paper or silicone baking mats. Set aside.

Using a cookie scoop (approximately 1 Tablespoon), remove dough from bowl and form into balls with your hand. Dough will become sticky again with the warmth of your hand, so try to be gentle and work quickly. Bake for 10-12 minutes. Cookies will look underdone. Allow cookies to cool on the baking sheet for about 5 minutes.

Press a Candy Cane Hershey's Kiss into the center and immediately put the baking sheet into the freezer for 10 minutes to prevent the Kiss from melting. Once completely cooled, you can allow cookies to come to room temperature on the baking sheet. Cookies can be kept in an airtight container at room temperature for 1 week. Cookies may be frozen-- use within 2 months. Raw cookie dough balls may be frozen up to 3 months. Do not thaw before baking and bake for 12-13 minutes.