Cook pasta according to package directions; drain and set aside.
Add oil to skillet; sauté mushrooms, red onions, garlic and red pepper flakes until lightly browned and tender.
Add Johnsonville Bias Sliced Italian Sausage; sauté for 2 minutes or until lightly browned.
Add chicken stock and bring to a simmer until sausage is hot.
Add the spinach; cook 1-2 minutes until wilted.
Add pasta and heat through. Add cheese and toss until cheese melts and coats pasta
Season to taste with salt and pepper.
Garnish with Parmesan cheese and red pepper flakes.