Mix all Cajun seasoning ingredients together in a small bowl. In an airtight container, combine chicken breast halves with 1.5 tablespoons of the Cajun seasoning and olive oil. Coat each piece thoroughly and refrigerate overnight for best results (minimum 30 minutes if short on time).

Heat a 12-inch pan or cast iron skillet over medium-high heat and melt 25g butter. Add marinated chicken and cook for 6-7 minutes per side until golden-brown crust forms and internal temperature reaches 165°F. Remove from pan and let rest for 5 minutes, then slice into strips.

In the same pan over medium heat, sauté chopped red onion for 3-4 minutes until softened. Add chopped garlic and cook for 1 minute until fragrant, being careful not to burn.

Sprinkle 0.5 tablespoon of Cajun seasoning into the pan and stir for 30 seconds to toast the spices. Add 3 cups of day-old rice and toss for 2-3 minutes until heated through and well coated with seasonings.

Lower heat to medium-low and add 15g butter to the pan. Once melted, add remaining 0.5 tablespoon of Cajun seasoning and slowly pour in milk while whisking constantly to prevent lumps.

Once milk is warmed (about 2 minutes), add cream cheese in small chunks and stir until completely melted and smooth. Add Parmesan cheese and continue stirring until sauce is silky and creamy. Add a splash more milk if sauce seems too thick.

Plate the Cajun rice, arrange sliced chicken strips on top, and generously drizzle the creamy sauce over everything. Garnish with freshly chopped parsley and serve immediately.