Cook the pasta in a large pot of salted water according to package directions. Drain and set aside.
In a large skillet over medium heat, add olive oil and sauté the smoked sausage until browned. Remove and set aside.
In the same skillet, add diced onion and cook until soft, about 3-4 minutes. Add garlic and red pepper flakes, cook for another 30 seconds.
Pour in chicken broth and bring to a simmer. Stir in heavy cream and Parmesan cheese. Cook until sauce slightly thickens.
Add the cooked sausage and drained pasta into the skillet. Stir everything to combine and heat through.
Season with salt and pepper to taste. Garnish with chopped parsley if desired and serve warm.