While croutons bake, cook penne until al dente according to package directions.
Turn the oven up to 400 degrees Fahrenheit after the croutons are done. Lightly grease a 13" x 9" casserole dish and add cooked penne, set aside.
In a large pan, heat 1 tbsp olive oil over medium-high heat and caramelize onions and mushrooms for about 10 minutes, season with salt and pepper to taste. Set aside in the casserole dish.
Pat diced chicken dry with a towel and season with salt and pepper to taste. In the same large pan, heat 1 tbsp olive oil over medium-high heat and cook diced chicken for 5-7 minutes until the center is no longer pink. Set aside in the casserole dish.
In the large pan, cook minced garlic in a teaspoon of olive oil for 60 seconds. Add white wine, sour cream, chicken broth, half of the mozzarella, thyme, 1 teaspoon salt, and ½ teaspoon black pepper. Bring to a simmer for 5 minutes. Pour into the casserole dish and mix with penne, chicken, mushrooms, and onions.
Top with remaining mozzarella, and croutons, and bake at 400 degrees Fahrenheit for 14-16 minutes until sauce is bubbling.