I find that it works best to first toast the entire muffin at least once before splitting it — if frozen, it may require a second pre-toasting. (foodforlife.com)
Be careful when mixing, you do not want to break the blueberries which would cause your entire muffin to be blue. (ahappyfooddance.com)
It's been around awhile, and with good reason because holy cow you dip the entire muffin in butter and then roll it all in cinnamon sugar. (thefoodcharlatan.com)