Preheat oven to 350 degrees and line 2 baking sheets with parchment paper.

In standing mixer or large bowl, beat butter and sugar until light and fluffy, about 2 minutes. Add in egg, milk, and vanilla and beat until combined.

In another bowl whisk together flour, cocoa, baking soda, and salt. Slowly add flour mixture into the butter mixture and beat until combined. Scrape down sides with spatula if needed.

Scoop out 1 Tbsp and form into round cookie dough balls. Roll in sprinkles, if desired, and completely cover dough ball. Repeat until all cookies are done.

Place on prepared baking sheet 2 inches apart and bake for 8 to 10 minutes.

Remove cookies and gently press candy kiss into center of each cookie.

Store in airtight container for 1 week.