Add the sausage meat to a Dutch oven or large soup pot. Cook over medium-high heat for about 5 minutes.
Incorporate the chopped onions and sauté with the sausage for an additional 5 minutes, or until the sausage is browned and the onions have softened.
Stir in the minced garlic, crushed red pepper flakes, and orzo, allowing the mixture to cook for 30 seconds.
Pour in the chicken broth and heavy cream. Bring the mixture to a gentle bubble, then reduce the heat to medium or medium-low. Cook uncovered for approximately 10 minutes, stirring frequently to prevent the orzo from sticking to the pot. Maintain a gentle simmer rather than a vigorous boil to ensure the liquid doesn’t evaporate too quickly.
Remove the pot from heat. Stir in the grated Parmesan and baby spinach. Cover the pot and let it rest for 3–5 minutes to allow the sauce to thicken and the spinach to wilt.
Season with salt and pepper to taste. Serve immediately.