Beat butter until creamy, then add sugars. Beat in eggs and vanilla. Combine flour, soda, and cocoa, then add to the butter mixture, beating well. If your dough is really soft, you can refrigerate for 30-60 minutes.
Roll into small balls ( a cookie scoop works great!), then into the 1-2 Tbsp. white sugar. Place on a cookie sheet that's been lined with parchment paper or foil and sprayed with cooking spray. Bake for 7-8 minutes at 375 degrees. If your oven tends to bake quickly, check them around 6 minutes--don't overbake!
As soon as they come out of the oven, press a Candy Cane kiss in the center of each cookie. Remove the cookies from the cookie sheet as soon as possible, so the kisses don't melt.