Heat olive oil in a large deep skillet or Dutch oven over medium-high heat. Add the sliced chicken sausage in a single layer and cook for 3-4 minutes per side, until golden brown. Use a slotted spoon to transfer the sausage to a plate and set aside.

Reduce heat to medium. Add the chopped onion to the same skillet and sauté for 4-5 minutes, until softened. Add the minced garlic and cook for another minute until fragrant.

Add the dry orzo to the skillet. Stir constantly for 1-2 minutes, until the pasta is lightly toasted and smells nutty.

Pour in about 1/2 cup of the chicken broth and scrape the bottom of the pan with a wooden spoon to release any browned bits (the fond). Add the remaining broth, sun-dried tomatoes, salt, pepper, and red pepper flakes. Stir to combine.

Bring the mixture to a boil, then reduce the heat to low, cover, and let simmer for 10-12 minutes, or until the orzo is al dente and has absorbed most of the liquid. Stir once or twice during cooking to prevent sticking.

Remove the lid. Stir in the heavy cream and the cooked sausage. Cook uncovered for 2-3 minutes, allowing the sauce to thicken slightly.

Turn off the heat. Add the fresh spinach in handfuls, stirring gently until it wilts completely. Stir in the grated Parmesan cheese until melted and the sauce is creamy. Taste and adjust seasoning if needed. Serve immediately with extra Parmesan on top.