Brown the Italian sausage in a skillet over medium heat, breaking it into crumbles. Drain excess fat and transfer the sausage to the slow cooker.
Add the diced potatoes, onion, and garlic to the slow cooker.
Pour in the chicken broth and stir in the Italian seasoning, salt, and black pepper.
Cover and cook on low for 7 hours, until the potatoes are soft.
Stir in the fresh spinach and heavy cream. Cover and cook for 15 more minutes until the spinach wilts.
Ladle into bowls and top each serving with grated Parmesan cheese.