Heat 1 tablespoon of sun-dried tomato oil in a large Dutch oven over medium heat. Add the chopped onions and minced garlic, cooking for about 3-4 minutes until softened and fragrant.

Stir in the tomato paste and sun-dried tomatoes, cooking for an additional 2 minutes while stirring constantly, allowing the tomato paste to deepen in color.

Pour in the chicken broth and heavy cream, followed by fresh basil, kosher salt, Italian seasoning, garlic powder, and crushed red pepper. Bring this mixture to a gentle boil, stirring occasionally, and let it simmer for about 12 minutes.

Add the uncooked medium shell pasta to the broth. Reduce the heat to medium-low and cook for approximately 12 minutes, stirring occasionally until the pasta is tender.

Lower the heat to low and stir in the spinach, shredded chicken, cream cheese, and Parmesan cheese. Keep stirring for about 5 minutes until the cheeses are perfectly melted and the chicken is warmed through.

Ladle the soup into bowls and garnish with extra Parmesan, fresh basil, and a sprinkle of red pepper flakes. Enjoy immediately with crusty bread or a fresh green salad on the side.