Cook Pasta: Bring a large pot of water to a boil. Add a generous pinch of salt. Cook the pasta according to the package directions. Drain and set aside.
Sauté Vegetables: Heat 1 tablespoon olive oil and 2 tablespoons butter in a large skillet over medium high heat. Once melted, add the diced onions and red bell pepper. Sauté until tender. Add the fresh garlic and cook another 30 seconds.
Make Roux: Add the flour to the skillet. Stir and cook for 1-2 minutes.
Make Sauce: Reduce the heat to medium low. Add the clam juice and heavy cream. Stir and cook until it starts to thicken. Add the Parmesan cheese and 1 tablespoon Cajun seasoning. Cook until the cheese melts.
Finish Pasta: Add the crawfish tails to the sauce. Cook for about 5 minutes. Then, add in the cooked pasta and toss to coat. Season with salt and pepper to taste. Keep warm over low heat while you grill the shrimp.
Blacken Shrimp: Season the shrimp with 1 tablespoon of oil and 1 tablespoon of Cajun seasonings. Heat the grill to high and cook the shrimp for 3-4 minutes per side.
Assemble: Place the grilled blackened shrimp on the skillet of pasta. Garnish with green onions. Serve.
Video
Notes
Every brand of Cajun seasoning is made a little differently, which is why I didn't give exact measurements for salt and pepper. Once your pasta dish is complete, taste the sauce and add salt and pepper to taste.