Prepare the rice per the package directions leaving slightly undercooked. Set aside to cool.
Preheat the oven to 350°F and spray a 13x9 inch baking dish with cooking spray.
In a medium saucepan, saute the diced onion and portabella mushrooms in 4 Tbsp of butter. Add seasoned salt and black pepper. Saute until the onions and mushrooms are softened and beginning to brown, Add the minced garlic. Saute for 1 minute longer. Remove from the stovetop.
In a large mixing bowl, combine the cooked onions and mushrooms, rice, chicken soup, celery soup, broth, mayonnaise, Parmesan and Mrs Dash. Mix well, then pour evenly into the baking dish.
In a small bowl, mix together melted butter, Panko, Parmesan and Mrs Dash seasoning. Sprinkle on top of the casserole.
Bake for 35-40 minutes or until golden and bubbly.
Notes
1/2 cup of frozen petite peas may be added, if desired.
Add cayenne pepper or red pepper flakes to your taste to add heat.
Omit Mrs Dash seasoning and use herbes de provence in its place.