Step 1Combine clarified butter and flour in saucepan. Bring to simmer over medium heat. Cook, stirring occasionally, until flour taste is gone, about 2 to 3 minutes. Remove from heat.
Step 2Bring milk to boil. Whisking constantly, add hot milk to flour mixture; continue whisking until smooth. Put saucepan over low heat. Simmer until smooth and thick, about 20 minutes, stirring frequently. Remove sauce from heat. Stir in cheese and nutmeg. Season with salt and pepper to taste. Taste and adjust seasoning; mixture should be well seasoned. Sauce will be thick.
Step 1Melt butter in large skillet over medium heat. Add green onion and onion. Cook until softened, about 3 minutes. Add crab meat and shrimp. Stir mixture. When warm, add all but 3/4 cup Bechamel Sauce. Mix well. Heat through. (Can be made a day ahead and refrigerated, covered airtight.)
Step 1Lay 2 crepes at a time on work surface. Spoon about 1/3 cup warm Crab and Shrimp Filling over one half of each. Fold in half to close. Place crepes side by side on greased baking sheets. Repeat with remaining crepes. Spoon remaining Bechamel Sauce over crepes, dividing evenly. (Can be made a day ahead and refrigerated.)
Step 2Tent with foil and bake at 350 degrees until warm, about 10 minutes. Remove foil. Bake 2 to 5 minutes more until sauce is bubbling. (Single servings can be reheated in microwave oven). Garnish with parsley and nutmeg. Serve warm.