Preheat the slow cooker if necessary; see the manufacturer's instructions. Put the chicken carcass into the slow cooker pot, breaking it in half if needed. Add the vegetables, herbs and boiling water, then add the peppercorns and salt.
Cover with the lid and cook on high for 5–7 hours. Lift the carcass out of the slow cooker pot and remove any meat; cut this into small pieces and reserve. Strain the stock, discarding the bones, vegetables and herbs, then pour the hot stock back into the slow cooker pot.
Add the shredded chicken, spinach, tomatoes and tortelloni. Replace the lid and cook for 20–30 minutes, still on high, until piping hot. Ladle the soup into bowls and serve sprinkled with a little grated Parmesan.