Add the sausage, oil and onion to a pot over medium-high heat. Sauté the sausage and onion for 3-4 minutes.
Add the garlic and orzo. Cook for 2-3 minutes to soften the garlic and toast the orzo.
Add the Italian seasoning, sun-dried tomatoes, lemon juice and Dijon mustard.
Add the chicken broth and cream or milk. Bring to a gentle boil. Continue cooking for about 10 minutes, until most of the liquid is absorbed and the pasta is cooked.
Stir in the parmesan and spinach. Season with salt & pepper as needed.