Preheat oven to 400 degrees F. Coat a 9x13 baking dish with non-stick cooking spray.
Cook pasta according to package and drain when finished.
Season diced chicken with seasoned salt. In a large skillet, heat 1 tablespoon of butter over medium heat. Add chicken to skillet and cook until browned. Place chicken in a bowl.
Add 2 tablespoons butter in the same skillet. Put in mushrooms, onions and thyme. Cook about 3 minutes or until mushrooms are slightly softened. Place in a bowl with chicken.
In the same skillet, add 3 tablespoons of butter. Whisk in flour then whisk in milk and chicken broth. Let simmer for 3-4 minutes to thicken. Stir in ½ cup of parmesan cheese. Season with salt and pepper.
Stir together pasta, vegetables, mushroom mixture, chicken and cheese sauce. Place in the prepared baking dish and top with remaining cheese and crushed butter crackers.
Bake until top is golden brown about 15-20 minutes.
**Leave the mushrooms out if you'd like!The calories shown are based on the recipe being served to 8 people, with 1 serving being 1/8 of the recipe. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**