Add 4 tablespoons of butter and 4 cloves of minced garlic to the pan, reduce heat to low, and cook until the garlic is fragrant, about 5 minutes. Pour in 1 1/2 cups of heavy cream and simmer for an additional 5 minutes.
Slice the cooked chicken into strips or small bites while the sauce simmers.
Mix in 2 cups of finely grated Parmesan cheese and 1 teaspoon of Cajun seasoning into the cream sauce, add the cooked pasta and stir to combine, thinning with reserved pasta water as needed.
Add the sliced chicken along with any accumulated juices and serve immediately.
Notes
For a spicier kick, increase the amount of Cajun seasoning in the chicken or sauce.