In a large pot, brown the Italian sausage over medium heat, breaking it up as it cooks. Once fully cooked, remove the sausage with a slotted spoon and set aside.
In the same pot, add the olive oil and sauté the onion until translucent, about 5 minutes. Add the minced garlic and cook for another minute until fragrant.
Pour in the chicken broth, bring to a boil, and then reduce to a simmer. Stir in heavy cream, oregano, basil, red pepper flakes, and season with salt and pepper.
Add the ditalini pasta to the pot and simmer until the pasta is al dente, about 8 minutes.
Return the cooked sausage to the pot and add the chopped spinach, cooking until the spinach wilts, roughly 2 minutes.
Off the heat, stir in the grated Parmesan cheese until melted and well incorporated.
Serve the soup hot, garnished with additional Parmesan and fresh parsley if desired.