With an electric mixer, beat margarine and sugar until smooth. Blend in egg yolk, milk, and vanilla extract.

Preheat oven to 350 Degrees F.

In a separate bowl, stir together flour, cocoa, and salt. Add the flour mixture to the butter mixture and mix until combined.

Wrap the dough in plastic wrap and refrigerate for at least one hour.

Roll the chilled dough into balls, approximately 1” in diameter. Roll each ball in sprinkles and place on a cookie sheet. Press any loose sprinkles in with your fingers.Use your thumb to make an indention in the top of each cookie.

Chill the prepared balls another 30 minutes. This keeps the cookies from running.

Bake at 350 degrees for 10-12 minutes, or until set.

Remove the cookies from the oven and immediately press a Hershey Kiss into the center. Allow to cool for 5 minutes, then transfer to a cooling rack.