Whether for family dinners or potlucks, chicken casseroles are always a winner. This chicken and spaghetti favorite is made extra cheesy with a blend of Swiss, cheddar, and Parmesan cheese.
Heat oven to 350 degrees F. Coat a 13 x 9 x 2-inch baking dish or casserole with nonstick cooking spray.
Cook spaghetti following package directions. Drain and rinse with cold water. Set aside.
In a large skillet, melt butter over medium-high heat. Add mushrooms, onion and garlic. Saute for 5 minutes. Add red pepper and sprinkle with flour. Cook, stirring, for 1 minute. Slowly stir in broth, heavy cream and milk. Simmer for 1 minute, until thickened.
Turn off heat; add cheeses. Stir until melted. Add salt, thyme, black pepper and chicken. Toss with cooked spaghetti and pour mixture into prepared dish.
Bake at 350 degrees F for 25 to 30 minutes until bubbling. Remove from oven and let stand for 10 minutes before serving.