Besides an appointment for your Christmas pedi, this is the easiest thing you will make during the holiday season. Really, it is.
I've seen lots of recipes that require more steps, like chopping pieces of peppermint candy in the food processor or making icing. They are lovely to look at, but not necessary.
Peppermint bark is easily found in discount stores such as Ross, Marshall's, TJ Maxx or Homegoods. After a false start to my holiday baking, I now have two one-pound boxes in my pantry, ready to go.
So... bake brownies according to package or recipe directions. While brownies are in the oven, unwrap the peppermint bark and break into pieces. The minute they come out of the oven, drop broken pieces of bark onto the top of the piping hot brownies in pan. Wait a minute or two for the candy to become soft and gooey.