Pat the salmon cubes and shrimp dry with paper towels. Toss both separately with the Cajun seasoning until evenly coated.
Heat the olive oil in a large skillet over medium-high heat. Add the salmon cubes and sear for 2-3 minutes per side until lightly browned. Remove the salmon and set aside.
Add the butter to the same skillet. Once melted, add the minced garlic and cook for 30 seconds until fragrant. Do not let the garlic burn.
Pour in the chicken broth and bring to a simmer, scraping up any browned bits from the bottom of the pan.
Reduce the heat to medium-low. Stir in the heavy cream and Dijon mustard. Let the sauce simmer gently for 3 minutes until it starts to thicken slightly.
Stir in the Parmesan cheese and black pepper. Continue stirring until the cheese is fully melted and the sauce is smooth.
Return the seared salmon to the skillet. Add the seasoned shrimp. Cook for 3-5 minutes, stirring occasionally, until the shrimp are pink and cooked through and the salmon flakes easily. Do not overcook the seafood.
Remove from heat. Taste the sauce and adjust seasoning if needed.
Serve immediately over rice or pasta, garnished with fresh parsley.
Notes
For best results, use a high-quality Cajun spice blend that includes paprika, cayenne pepper, and oregano.
If you prefer a thicker sauce, simmer the cream mixture for an extra minute or two before adding the seafood.
This dish pairs well with steamed asparagus or a simple green salad.