Cook green beans per package directions. Drain water and set aside.
In a large skillet add your butter, celery, onion, mushrooms and chicken better that bouillon. Cook until onions and celery and soft.
In a large bowl combine your heavy cream, spices and mayonnaise and whisk together. Add your onion mixture, chicken, green beans, ½ of your cheese and stir well.
Pour into a 9x13 casserole dish. Spread out your mixture evenly. Sprinkle the other half of your shredded cheddar cheese and place in a pre-heated 400° oven. Cook for 18-20 minutes or until the casserole is bubbling in the middle.
Remove from the oven and sprinkle your Crispy Onions over the top.