Melt butter in a skillet over medium heat. Sauté onion, celery, parsley, and mushrooms in butter for approximately 10 minutes, until onions are translucent.
In the slow cooker, gently combine bread cubes, vegetable-butter mixture, and the seasoning package (included with the stuffing mix).
Pour in broth.
Carefully mix in beaten eggs.
Cook on high for 45 minutes.
Stir gently. Reduce heat to low, and cook for 4 hours.
If the stuffing is ready before the turkey, reduce heat to warm until ready to serve.
Notes
Storage: Store stuffing in an airtight container in the fridge for up to three or four days or in the freezer for up to three months.Reheating: Add a splash of broth, then bake in an oven-safe dish at 350℉ for 20-30 minutes. Variations: your family's favorite stuffing mix-ins (like sausage and apples), just keep the ratios roughly the same.Vegetarian: substitute vegetable broth and double-check your stuffing mix to make sure it is vegetarian.Buy two boxes of stuffing, and buy them early in the holiday season to avoid them being sold out.Use a crock-pot liner if using a gluten-contaminated slow cooker.