Preheat oven to 350°.
Wash, sliced and cook mushrooms in skillet until tender, drain and set mushrooms aside.
In the same skillet melt 1/4 stick of butter and add water, then combine with stuffing mix, celery and onion.
In a separate bowl, combine cheddar cheese and yogurt.
In a greased 13x9 inch casserole dish, layer mushrooms, yogurt mixture, then stuffing.
Repeat, ending with stuffing.
Cut remaining 1/4 stick of butter into small pads and scattered on top.
Casserole may be made ahead and refrigerate.
Before cooking, sprinkle with 1/4 cup of parmesan.
Bake for 30 minutes.