In a large pot, heat olive oil over medium-high heat. Add ground Italian sausage and cook, breaking it apart with a spoon, until browned; drain any excess grease and set the sausage aside.

To the same pot, add chopped onion and cook until softened, about 5-7 minutes. Stir in minced garlic and cook for another minute until fragrant.

Pour in chicken broth and undrained diced tomatoes, bringing the mixture to a simmer. Add the cooked Italian sausage back into the pot.

Stir in ditalini pasta and cook according to package directions until al dente, usually 8-10 minutes. Ensure the pasta is tender but still has a slight bite.

Reduce heat to low, then stir in heavy cream and grated Parmesan cheese until the cheese is melted and the soup is creamy. If using, add fresh spinach and cook until wilted.

Season the soup with salt and black pepper to taste. Serve hot, garnished with extra Parmesan cheese if desired.