Heat the Oil: In a large pot or Dutch oven, heat 1 tablespoon of olive oil over medium heat.
Cook the Sausage: Add the crumbled Italian sausage and break it apart with a spoon. Cook until browned on all sides, about 5–7 minutes.
Remove Excess Grease: Transfer the browned sausage to a bowl using a slotted spoon, leaving any browned bits in the pot.
Sauté the Onion: Add the diced onion to the pot and cook for 2–3 minutes until soft and translucent.
Add the Garlic: Stir in the minced garlic and cook for another minute until fragrant.
Build the Broth: Pour in 4 cups of chicken broth and add the drained diced tomatoes. Bring the mixture to a gentle simmer.
Return the Sausage & Season: Add the browned sausage back into the pot. Sprinkle in 1 teaspoon of Italian seasoning, optional 1/4 teaspoon red pepper flakes, and season lightly with salt and freshly ground black pepper.
Cook the Pasta: Stir in 1 cup of ditalini pasta, ensuring it is fully submerged in the broth. Cook according to the package instructions until al dente, about 8–10 minutes.
Incorporate the Cream: Lower the heat and gradually stir in 1 cup of heavy cream (and 4 oz of optional cream cheese, if using) until fully melted and the broth is smooth and creamy.
Add Fresh Greens: Stir in 2 cups of fresh spinach and let it cook for 2–3 minutes until wilted.
Adjust Seasoning: Taste the soup and adjust salt and pepper as needed.
Serve and Garnish: Ladle the hot soup into bowls and garnish with chopped fresh parsley (or basil) and extra grated Parmesan cheese.