Heat a large pot or skillet over medium-high heat. You want it to be large enough to fit the entire dish, so make sure it’s big! Season the chicken with the cajun seasoning, covering it completely. Sprinkle the chicken pieces with the flour and coat them thoroughly. I usually begin to heat the water for the pasta here and once it boils, add the pasta.
Add the oil and 2 tablespoons butter to the skillet. Once sizzling, add the chicken and cook until crispy and deeply browned, flipping once or twice. This will take about 8 to 10 minutes for the chicken to be cooked through. Once cooked, remove it and set it on a plate. Reduce the heat to medium-low and add 2 more tablespoons of butter to the skillet. Toss in the onions and peppers with a pinch of salt and pepper and stir well. Cook for 5 minutes, until they soften. Add in the other 2 tablespoons of butter and the mushrooms, stirring well. Cook for 5 to 6 more minutes, so the mushrooms soften. Stir in the garlic.
Increase the heat to medium-high again. Pour in the chicken stock slowly while stirring with a wooden spoon and scraping the bottom of the pot. Bring the stock to a boil and cook for 5 to 6 minutes. Reduce the heat once more and stir in the cream. Add the chicken to the pot along with the pasta. Taste and season additionally if needed. Sprinkle with the parsley and serve immediately.