Cook the 1 pound fettuccine pasta in salted boiling water until al dente. Follow the instructions on its packaging. Drain in a colander, drizzle with a little olive oil to prevent sticking and set aside.
Heat a high-sided skillet over medium-high heat, sear the ½ pound smoked andouille sausage on both sides until the exterior is browned and crispy. Remove from the pan, slice and set aside.
Season the 1 pound raw large shrimp with the 2 teaspoons Cajun seasoning in a mixing bowl. Toss to coat.
Melt the 2 tablespoons salted butter in the same skillet that you cooked the sausage in over medium heat.
When the butter bubbles, add the shrimp, and cook on both sides until pink and cooked through, about 2-3 minutes per side, depending on the size of the shrimp.
Remove the shrimp from the skillet, and set aside.
Add the 4 garlic cloves, cooking until fragrant and lightly colored, about 1-2 minutes.
Lower the heat to low, and pour in the 2 cups heavy cream and 1 cup whole milk. Add the grated 1 ½ cups parmesan cheese, and stir until smooth and creamy, about 4-5 minutes.
Give the sauce a taste, and add extra salt and pepper, if necessary.
Add the pasta to the sauce, and toss until coated.
Serve the pasta in bowls, then top with the shrimp and sliced andouille sausage.
Garnish with Fresh parsley and more Cajun seasoning, if desired, and enjoy immediately.
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