Bring large pot with water to a boil. Add a pinch of salt and pasta, then cook for 8-10 minutes or until pasta is al dente. Drain and set aside.
Preheat another large pot on medium-high heat and add butter. Add onion and garlic, saute for 3 minutes, stirring occasionally. Add chicken and saute for another 5 minutes, stirring occasionally.
Add flour and stir to coat. Add chicken broth and cook until incorporated and smooth, about 3 minutes, stirring often.
Add sun dried tomatoes, Italian seasoning, salt, pepper, red pepper flakes, heavy cream and Parmesan cheese. Stir, bring to a boil, reduce heat to low and simmer for 10 minutes, stirring occasionally.
Add spinach and pasta, then mix gently.
Garnish with parsley or basil and serve hot.
Notes
Store: Refrigerate in an airtight container for up to 5 days.
Freeze: I do not like to freeze pasta because it doesn't thaw well but you can freeze it in an airtight container for up to 3 months.