Sauté the aromatics: Heat 2 tablespoons olive oil in a large pot over medium heat.
Add onion, carrots, and celery with a pinch of salt. Cook 6–8 minutes, stirring, until softened and lightly golden. Add garlic and cook 30 seconds more.
Bloom the herbs: Stir in thyme, Italian seasoning (if using), and a few grinds of pepper.
Let them toast for 30 seconds to release flavor.
Optional thickener: Sprinkle in 1–2 tablespoons flour and stir for 1 minute to make a light roux. This gives the soup a silkier, slightly thicker body.
Add broth and simmer: Pour in the chicken broth and add the bay leaf. Bring to a gentle boil, then reduce to a simmer for 10 minutes to let the flavors meld.
Cook the tortellini: Add the tortellini to the simmering broth.
Cook according to package directions, usually 3–5 minutes, until just tender. Don’t overcook—tortellini should be plump with a slight bite.
Add chicken and greens: Stir in the cooked chicken and spinach. Simmer 2–3 minutes, just until the chicken is warmed through and the spinach wilts.
Finish with cream: Lower the heat to just below a simmer.
Stir in the cream, starting with 3/4 cup. Warm gently for 1–2 minutes. Do not boil after adding cream.
Brighten and season: Add a squeeze of lemon juice (start with 1–2 teaspoons) and a pinch of lemon zest.
Taste and adjust salt and pepper. Add red pepper flakes if you like a little heat.
Serve: Ladle into bowls and top with grated Parmesan. Crack black pepper over the top for a final touch.