Cook pasta according to package instructions. Drain and set aside
Saute veggies: Add butter to dutch oven or pot over medium heat. Once melted, add mushrooms, spreading them apart into an even layer. Sauté for several minutes on medium high heat, then turn and cook on the other side for a few minutes. Add celery and onion and cook, stirring occasionally, for 5 minutes. Add garlic and cook for 30 seconds. Add ¼ cup white wine to deglaze the pan and cook for 1-2 minutes. Remove contents to a bowl and set aside.
Make sauce: Add remaining ¼ cup butter to the pan and stir in flour. Cook for 1 minute, stirring constantly. Gradually stir in milk and chicken broth until smooth. Season with chicken bouillon, season salt, pepper, and paprika. Once sauce begins to slightly thicken, remove from heat. Taste and adjust seasonings if needed.
Combine: Stir in ½ cup mozzarella cheese and ¼ cup parmesan cheese. Stir in sautéed vegetables. Add noodles, cooked chicken and parsley and use tongs to toss and coat everything in sauce.
Bake: Pour into casserole dish and smooth into an even layer. Top with remaining ½ cup mozzarella cheese and ¼ cup parmesan cheese. Bake at 375 for 25 minutes.
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Notes
Pasta: For a healthier version, use whole wheat spaghetti.Turkey Tetrazzini: Sub cooked leftover turkey if you want.Make Ahead Instructions: Sauté the vegetables and cook the sauce. Store the sauce and cooked pasta separately in the fridge, and then combine when ready to bake.Freezing Instructions: The compiled casserole may be frozen for up to 3 months, but it wont be very "saucy" after baking, since the pasta will have soaked up some of the sauce. Thaw completely before baking.