Heat the olive oil in your Dutch oven over medium heat, then add the onions and garlic. Cook until the onion softens and the mixture becomes fragrant, usually about 3–4 minutes.
Stir in the sun-dried tomatoes and tomato paste. Let them cook together for a minute or two so the flavors deepen and the tomato paste caramelizes slightly.
Pour in the chicken broth and season with salt, pepper, Italian seasoning, and crushed red pepper. Allow the soup to come to a gentle boil so the flavors meld.
Add the pasta directly into the boiling broth and cook until just al dente. It will soften further when the remaining ingredients are added.
Reduce the heat, then add the shredded chicken, chopped spinach, half & half, Boursin cheese, and a portion of the Parmesan. Stir until the cheeses melt and the soup becomes creamy.
Serve hot and top each bowl with extra Parmesan, red pepper flakes, or fresh herbs like parsley or basil. It adds a beautiful finish.