When you open the can of carrots, run the blade of a paring knife through them right in the can so that you've reduced them to tiny bits without mashing them. Empty it then into a Dutch oven. Add the mushrooms; set aside.
Empty the can of broth into the blender and add the celery along with the sage, poultry seasoning, bouillon powder and margarine. Blend a few seconds on high speed, only until celery is finely minced.
Meanwhile, add the English muffin cubes, (crumbs too), croutons, parsley and onion to the Dutch oven. Pour blender mixture over and stir to combine with rubber bowl scraper until completely moist.
Cover with a lid and bake at 350 degrees about 45 minutes to an hour or until piping hot.
Refrigerate leftovers to use within a week. Freeze to use within 4 months.