Melt butter in 5-quart Dutch oven over medium-high heat. Saute onions, celery, bell peppers and garlic until very wilted. Add bay leaf and Rotel tomatoes, along with Cajun seasoning, salt and paprika. Cook over medium heat about 5-10 minutes. Add crawfish and shrimp. Cover and cook about 10 minutes, stirring often.
Add parsley and 2 tablespoons flour stirred into enough cold water to make 1/2 cup. Quickly add flour mixture to seafood and stir. Heat until slightly thickened. Serve over angel hair pasta and top with grated Parmesan cheese.
Cajun Country -- New Iberia, Louisiana