01 - Preheat oven broiler on high setting.
02 - Cook elbow macaroni in a large pot of salted boiling water until al dente. Drain thoroughly and set aside.
03 - In a mixing bowl, toss shrimp with olive oil, Cajun seasoning, smoked paprika, cayenne pepper, and salt until evenly coated.
04 - Heat a large skillet over medium-high heat. Sauté seasoned shrimp for 2–3 minutes per side, or until shrimp turn pink and are just cooked through. Transfer shrimp to a plate and keep warm.
05 - In a large saucepan over medium heat, melt 3 tablespoons of butter. Add flour, whisking constantly, and cook for 1 minute to form a blond roux.
06 - Gradually pour in whole milk while whisking. Simmer, stirring frequently, until sauce thickens slightly, about 4–5 minutes.
07 - Reduce heat to low. Add cheddar cheese, Monterey Jack, cream cheese, garlic powder, onion powder, black pepper, and salt to taste. Stir until all cheese has melted and sauce is smooth.
08 - Fold cooked macaroni into cheese sauce, mixing until pasta is thoroughly coated.
09 - Gently fold cooked Cajun shrimp into the pasta, reserving a few shrimp for final garnish if desired.
10 - Pour mixture into a large ovenproof skillet or casserole dish, spreading evenly.
11 - Combine panko breadcrumbs, melted butter, and Cajun seasoning in a small bowl. Sprinkle mixture evenly over macaroni.
12 - Broil for 1–2 minutes, watching carefully, until breadcrumbs are golden and crisp.
13 - Garnish with chopped fresh parsley and reserved shrimp. Serve immediately while hot.