In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until softened.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the ground chicken to the pot, breaking it up with a spoon. Cook until browned and cooked through, about 6-8 minutes.
Season the mixture with Italian seasoning, salt, and black pepper. Stir to combine.
Pour in the chicken broth and diced tomatoes. Bring to a simmer and let cook for 10 minutes.
Reduce the heat to low and stir in the heavy cream, spinach, and Parmesan cheese. Cook for another 5 minutes until the spinach is wilted and the soup is heated through.
If desired, stir in fresh basil just before serving.