In a medium bowl, mix chicken, panko, egg, Italian seasoning, salt, pepper, garlic powder, 1/2 cup tomatoes, and 1/2 cup Parmesan. Form into 18 meatballs.
In the slow cooker, combine onion, garlic, broth, wine, and tomato oil; season with salt. Add meatballs. Cover and cook on high for about 4 hours until meatballs are cooked through.
Preheat the broiler. Transfer meatballs to a foil-lined baking sheet using a slotted spoon.
Add gnocchi and remaining tomatoes to the slow cooker. Cover and cook on high for about 20 minutes until gnocchi is tender.
Broil meatballs until golden brown, about 6 to 8 minutes, turning halfway through.
Stir spinach, cream, and 1/4 cup Parmesan into the slow cooker. Return meatballs. Cover and cook until spinach wilts, about 5 minutes more.
Serve gnocchi and meatballs in bowls, topped with additional Parmesan. Enjoy the Tuscan goodness!