The Best Creamy Chicken, Spinach and Mushroom Tortellini Soup

1 1/2 Tbsp olive oil
1 1/3 cups chopped yellow onion (1 medium)
1 1/3 cups diced carrots (about 3 medium)
6 - 8 oz cremini mushrooms , sliced
3 cloves garlic , minced
4 1/2 cups low-sodium chicken broth
1 lb bonless skinless chicken breasts , pounded evenly to about 1/2-inch thickness
1 tsp dried oregano
1/2 tsp dried thyme
Salt and freshly ground black pepper
1/4 cup unsalted butter , sliced into 1 Tbsp pieces
1/3 cup flour
2 1/2 cups milk
9 oz refrigerated three cheese tortellini
4 oz fresh spinach (4 cups)
1/3 cup heavy cream
Finely shredded parmesan cheese , for serving

Heat olive oil in a large pot over medium-high heat. Add onion, carrots and mushrooms and saute 3 minutes then add garlic and saute 1 minute longer. Add in chicken broth, chicken, oregano and thyme and season with salt and pepper. Bring to a boil, then reduce heat to medium-low, cover pot with lid and allow to simmer 10 - 15 minutes until chicken is cooked through (it should register 165 degrees in center on an instant read thermometor).
While chicken is cooking, melt butter in a medium saucepan over medium heat. Add flour and cook, whisking constantly 1 minute. While whisking vigorously slowly pour in milk. Season with salt and pepper and bring mixture just to a light boil, stirring constantly. Remove from heat and set aside.
Remove cooked chicken from soup and transfer to a cutting board, let rest 5 minutes then cut into pieces. Meanwhile, add tortellini to soup in pot, cover pot with lid and allow to boil over medium heat about 7 minutes (or time directed on package) adding in spinach during last 1 minute. Stir in chicken, white sauce and cream. Serve warm with parmesan cheese.
Recipe source: Cooking Classy