Make your Cajun seasoning and set aside. (You will have extra for another recipe)
Set a large pot of water to boil and cook the pasta two minutes less than what is indicated on the box. Drain but do not rinse so the starch stays on the pasta. This will help the sauce stick to it better.
In the same pot where you boiled your pasta, melt butter over medium heat. Add the mushrooms, and sauté until they get shiny. Then add the onion and peppers.
Cook for a few minutes until the veggies begin to get golden. Add the minced garlic and sauté for another minute or two, stirring often.
Mix in the red pepper flakes, Cajun seasoning, salt and pepper, stirring to coat the spices on the veggies.
Add the chicken stock, heavy cream and Parmesan cheese. Simmer for a few minutes until heated through.
Add in the cooked pasta
Let the sauce thicken and stir for about 5 minutes, or until the sauce coats the pasta well.
Serve the pasta topped with chopped parsley and additional Parmesan if desired.