Melt butter in a large skillet and add chopped onion, celery and parsley.
In a very large bowl, mix together all of the sourdough bread cubes, cut into a size that you prefer for stuffing. You can also put the sourdough in your food processor and make it into large crumbles.
Pour the sauteed onion, celery, parsley and butter over the bread cubes. Add all seasonings and toss well.
Add just enough broth to moisten it well. Too much broth which will make it soggy. More broth can be added part way through the cooking process if it looks too dry, but you can’t take it back out!
Spray the slow cooker and lightly pack the stuffing into it. Cover. Cook on high for 45 minutes and then low 3-4 hours. Stir a couple times.
Notes
The optional ingredients should be added after your turn the slow cooker down to low.
Feel free to use any flavor of sourdough bread - plain, wheat, multi-grain, or purple sweet potato, or any combination of these.