Bring a large pot of salted water to a boil and cook the pasta until just shy of al dente; reserve 1 cup pasta water and drain.

In a large skillet over medium-high heat, melt 1 tbsp butter and brown the andouille sausage slices; remove and set aside.

Add another tablespoon of butter to the same pan and cook the shrimp until just opaque; remove and set aside.

Add the remaining butter and sauté diced onion, bell pepper, and mushrooms until softened.

Stir in minced garlic and cook briefly until fragrant.

Pour in crushed tomatoes and Cajun seasoning; simmer for a few minutes.

Add the heavy cream, paprika, and remaining Cajun seasoning; stir and simmer gently until the sauce slightly thickens.

Return the sausage and shrimp to the sauce, and fold in the crawfish tails if using; heat through.

Add the cooked pasta and toss to coat, adding reserved pasta water a little at a time to achieve a glossy, silky sauce.

Finish with a squeeze of lemon juice and taste for seasoning. Serve hot, garnished with freshly grated Parmesan and parsley.