Raise heat to medium-high and spray with cooking oil again. Add in mushrooms and saute until slightly brown and soft, about 4 minutes. Move mushrooms to the sides of the pan, then add in onion, peppers, and garlic. Add a pinch of salt to the veggies and cook until slightly softened, about 5-7 minutes.
When veggies are slightly soft, add pasta, chicken broth, almond milk, and Cajun seasoning. Bring to a boil, cover with lid, and reduce to a simmer. Cook for about 12 minutes, or until pasta is slightly soft.
Remove lid. Raise heat to medium-high. Stir in half and half, parmesan cheese, salt, and pepper. Continue to cook, stirring constantly, until sauce has thickened to your liking, about 4-6 minutes.
Taste for seasoning. Add salt and pepper to taste. If you like extra heat, add in some dashes of cayenne pepper or red pepper flakes.
Taste the pasta and adjust salt and pepper to your liking. Slice the chicken and serve it over the pasta.