I gently twist each Golden Oreo apart instead of pulling it, which keeps the frosting layer intact on one side. I set the plain cookie halves aside to snack on later, since only the frosted half gets used in the finished cookie.
On the frosted half of each cookie, I press a Bugle into the icing at an angle so it looks like the curved opening of a cornucopia. I always keep a handful of extra Bugles nearby since some break or don't curl the way I want.
I press mini M&M's into the frosting around the base of the Bugle, building outward so it looks like the candy is spilling out of the horn. I like mixing in a few extra colors here to make each cookie look slightly different.
If any M&M's feel wobbly, I dab a little leftover frosting underneath with my fingertip or a toothpick. This little trick keeps everything in place even if the cookies get jostled on the way to a gathering.
I let the finished cookies sit for about five minutes so the frosting firms back up around the candy. After that, they're ready to arrange on a platter and bring straight to the table.