Melt butter in large stock pot. Add onion, garlic and sausage. Cook, stirring frequently, for 1-2 mins or until sausage is slightly browned. Remove pot contents and set aside.
Add broth, diced tomatoes, tomato paste, and seasonings to stock pot and stir together. Bring liquid to a boil, add pasta and cook according to pasta box instructions.
When pasta is fully cooked, stir in cream cheese and sausage/onion/garlic mix. Cook another 1-2 mins until cheese is melted. Top with parmesan cheese and red pepper flakes (optional).
Video
Notes
Lightly brown sausage. Since the chicken sausage is fully cooked, you'll simply want to sear it for a few minutes with the garlic and onion until only lightly browned.