Heat butter in a large pot over medium heat and cook onions until soft, about 3-4 minutes.

Add flour and seasonings (poultry seasoning, dried rosemary) and cook 1 minute more.

Stir in chicken broth a bit at a time, whisking until smooth after each addition.

Add celery, carrots, potatoes, and bay leaf. Bring to a boil, reduce heat to a simmer, and cook covered for 17 minutes or until vegetables are tender.

Stir in the cooked chicken, tortellini, and heavy cream, simmer an additional 5 minutes uncovered or until tortellini is cooked through.

Stir in peas, discard bay leaf and season with salt and pepper to taste. Let rest 2-3 minutes to heat the peas.