In a medium bowl, toss the cubed chicken with 1 tablespoon of Cajun seasoning, garlic powder, onion powder, and cayenne pepper (if using). Ensure all chicken pieces are evenly coated.

Heat 2 tablespoons of olive oil in a large skillet or Dutch oven over medium-high heat. Add the seasoned chicken to the hot skillet in a single layer, being careful not to overcrowd the pan. Cook for 5-7 minutes, stirring occasionally, until the chicken is browned and cooked through. Remove the chicken from the skillet and set aside.

While the chicken cooks, bring a large pot of heavily salted water to a rolling boil. Add 1 tablespoon of olive oil to the water to prevent sticking.

Add the fettuccine pasta and cook according to package directions until al dente. Reserve about 1 cup of the pasta cooking water before draining. Drain the pasta and set aside.

In the same skillet (no need to clean) over medium heat, melt the unsalted butter. Add the minced garlic and sauté for 1 minute until fragrant, being careful not to burn it.

Pour in the heavy cream and milk. Bring the mixture to a gentle simmer, stirring frequently. Reduce heat to low.

Stir in the remaining 0.5 tablespoon of Cajun seasoning, salt, and black pepper.

Gradually add the freshly grated Parmesan cheese, whisking constantly until the cheese is melted and the sauce is smooth and slightly thickened. If the sauce is too thick, add a splash of the reserved pasta water until desired consistency is reached.

Add the cooked chicken and drained fettuccine pasta to the Alfredo sauce in the skillet. Toss gently to combine, ensuring all the pasta and chicken are coated in the creamy sauce.

Serve immediately, garnished with fresh chopped parsley and extra grated Parmesan cheese, if desired.