Melt the butter in a large Dutch oven or soup pot set over medium heat.

Add the finely chopped onion and cook, stirring, until it just begins to brown, about 3–4 minutes.

Stir in the garlic, Italian seasoning, salt, pepper, and chili flakes. Cook for about 1 minute until fragrant.

Pour in the chicken broth. Add the uncooked chicken breasts and the chopped sun-dried tomatoes. Increase the heat to medium-high, bring to a simmer, then reduce the heat to medium-low, cover, and cook for approx. 12–15 minutes or until the chicken is fully cooked (internal temp 165°F).

Meanwhile, cook the pasta in a large pot of boiling salted water according to package directions; drain and set aside.

Remove the cooked chicken from the soup, shred it using two forks, then return the shredded chicken to the pot.

In a small bowl, whisk together half-and-half and cornstarch until smooth. Stir this into the soup pot and cook for 1–2 minutes until the broth slightly thickens.

Add the cooked pasta and chopped spinach into the soup. Stir and heat through until the spinach is wilted and everything is well-combined.

Taste and adjust seasonings if needed. Serve hot, garnished with dollops of ricotta, a sprinkle of Parmesan, and some shredded mozzarella on top.