To make ahead, prepare as above but do not bake. Cover and refrigerate up to 24 hours.
Remove stems from mushrooms and dust off caps with a dry towel. Chop mushroom stems. Melt 2 Tbsp. butter in a saucepan and brush mushroom caps with melted butter. Place topside down in a shallow baking pan. Heat remaining butter, add chopped mushroom stems, onion and garlic and cook until tender. Remove to a bowl. While warm, add cream cheese and stir to combine. Stir in Parmesan, Sage & Savory Stuffing Seasoning, parsley flakes and bread crumbs. Spoon 1 Tbsp. of stuffing mixture onto each mushroom cap. Place under broiler for 7 to 9 min. or until golden brown and hot.