Prep your veggies: Dice the onion and slice the carrots and celery. Mince the garlic.
Keep the tortellini and greens in the fridge for later.
Optional flavor boost: In a small skillet, warm olive oil over medium heat and sauté the onion, carrots, and celery with a pinch of salt for 5 minutes. Add garlic for the last 30 seconds. This step adds depth but isn’t required.
Load the slow cooker: Add chicken, vegetables, garlic, broth, thyme, Italian seasoning, bay leaf, and a generous pinch of salt and pepper.
Cook low and slow: Cover and cook on Low for 6–7 hours or High for 3–4 hours, until the chicken is tender and shreds easily.
Shred the chicken: Remove chicken to a cutting board and shred with two forks.
Discard the bay leaf. Return the shredded chicken to the slow cooker.
Add tortellini: Stir in the tortellini and cook on High for 15–20 minutes, or until they float and are tender. Don’t overcook.
Finish with greens: Stir in spinach (or kale) and let it wilt for 2–3 minutes.
Add parsley and a squeeze of lemon if using. Taste and adjust seasoning.
Serve: Ladle into bowls and top with grated Parmesan and cracked black pepper.