Boil the Pasta: Bring a large pot of salted water to a boil. Add the fettuccine and cook according to the package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta in a colander and set aside.
Create the Creamy Base: Pour in the heavy cream and chicken broth, stirring well to combine. Bring the mixture to a gentle simmer.
Add the Spices: Stir in the Cajun seasoning, salt, black pepper, and cayenne pepper (if using). Let the sauce simmer for about 5 minutes to thicken.
Cook the Shrimp: Add the shrimp to the skillet, cooking for about 3-4 minutes until they turn pink and are cooked through.
Combine Crab and Pasta: Gently fold in the lump crab meat and cooked fettuccine, adding a bit of the reserved pasta water if the sauce needs to be loosened up.
Final Warm-Up: Cook everything together for an additional 2 minutes, ensuring everything is combined and heated through.
Garnish and Serve: Remove from heat and garnish with chopped parsley. Serve hot with grated Parmesan cheese on the side.
Notes
Taste as you go and adjust spices based on personal preference. Use canned lump crab meat if fresh is unavailable.