Soften cream cheese by resting on counter, or by placing in microwave for 20-30 seconds. Set aside.
Heat oil and butter in saucepan over medium heat. Add onions and saut茅 for 5 minutes. Stir in garlic and cook for another 30 seconds. Add mushrooms and Italian seasoning. Cook for 5-6 minutes, until the mushrooms have released their water and it is cooked off.
Add flour and cook for 1 minute, stirring constantly. Add 2 cups of chicken stock and stir until all flour is dissolved. Then add remaining 4 cups of stock.
Add milk and Mafalda pasta. Increase heat and bring to boil. Once boiling, reduce heat to simmer. Stir and cover, with lid slightly ajar. Cook for 10-12 minutes, until pasta is tender.
Add chicken and cream cheese (cut into small pieces). Stir until cream cheese is completely combined.
Stir in Parmesan cheese and spinach. Mix until the cheese is completely incorporated and the spinach is wilted. Season to taste.
If the soup is too thin, cook until it is reduced to desired consistency. If it is too thick, add some stock or milk.
