I've also heard of people calling them Santa Buttons. They are SUPER easy and fast to make, and not to mention delicious!
Any kind of Hershey Kiss, Reese's peanut butter cups, or Rolos
Preheat your oven to 300 degrees. Unwrap your candies and place them on a baking sheet (I put foil on top because it's easier to peel them off in the end). Put a pretzel ring on each candy (for peanut butter cups, the pb cup will have to go on top of the pretzel). It's ok if the pretzel isn't perfectly round.
Pop them in the oven for 3 minutes. Around the 1 minute mark I open the oven and shake the cookie sheet around a little bit to get the chocolate moving in the middle of the pretzel ring. When the time is up and you get them out of the oven, I move the tray back and forth again to move the chocolate around. Place an M&M on each, pressing down slightly.
Refrigerate for 5-10 minutes or until chocolate is firm. Store at room temperature.