Add the Italian sausage to a large Dutch oven over medium heat. Cook until no longer pink, about 5 minutes, breaking the sausage apart as it cooks. Drain grease and set aside.

Add olive oil, diced onion, diced bell pepper, salt, pepper, and crushed red pepper flakes to the pot. Cook until tender, about 5 minutes. Add the garlic and cook one minute more.

Return the cooked sausage to the pot, along with the chicken stock, crushed tomatoes and Italian seasoning. Add additional salt and pepper, to taste, if needed.

Bring to a boil, then add the orzo pasta. Simmer over medium low for 8-10 minutes, stirring often, until orzo is just tender.

Stir in the spinach and heavy cream. Return to a boil and simmer until spinach is wilted and orzo is fully cooked. Top with Parmesan cheese to serve, if desired.