1. Sauté the aromatics: Heat the olive oil in a large pot or Dutch oven over medium heat. Add the cubed chicken and cook until lightly browned on all sides, about 5-7 minutes. Remove the chicken from the pot and set aside. Add the chopped onion, diced carrots, and diced celery to the same pot. Cook, stirring occasionally, until the vegetables soften, about 5-7 minutes. The onion should become translucent.

2. Add the garlic and seasoning: Stir in the minced garlic and dried Italian seasoning. Cook for another minute until fragrant, being careful not to burn the garlic.

3. Build the broth base: Pour in the chicken broth and the can of undrained diced tomatoes. Return the cooked chicken to the pot. Stir in the salt and black pepper. Bring the mixture to a gentle boil, then reduce the heat to low, cover, and simmer for 10 minutes to allow the flavors to meld and the chicken to cook through.

4. Cook the tortellini: Increase the heat back to medium-high and add the refrigerated cheese tortellini to the simmering soup. Cook according to package directions, usually 3-5 minutes, until the tortellini are al dente and float to the top. Do not overcook, or they will become mushy.

5. Stir in the cream and spinach: Reduce the heat to low. Stir in the heavy cream and chopped fresh spinach. Cook for just 1-2 minutes, or until the spinach wilts. Avoid boiling the soup once the cream is added to prevent it from curdling.

6. Serve and enjoy: Ladle the hot soup into bowls. Garnish each serving with a sprinkle of grated Parmesan cheese.