Prepare Crepe Batter: In a mixing bowl, whisk together 1 cup of all-purpose flour and 2 large eggs until smooth. Gradually mix in 1 cup of milk and ½ cup of water, ensuring a lump-free consistency. Add a pinch of salt and 2 tablespoons of melted butter to enhance flavor. Let the batter rest for 15 minutes.

Cook the Crepes: Heat a non-stick frying pan over medium heat and lightly coat it with butter or oil. Pour ¼ cup of the batter into the pan, swirling to cover the bottom evenly. Cook for 1-2 minutes or until the edges lift slightly and the bottom is golden. Carefully flip and cook for another 1-2 minutes until the second side is lightly browned. Transfer the crepes to a plate and cover to keep warm.

Sauté the Seafood Filling: In a skillet, heat 2 tablespoons of olive oil over medium heat. Add 1 chopped onion and 2 minced garlic cloves, sautéing until translucent, about 3-4 minutes. Add 1 cup of deveined shrimp and ½ cup of lump crab meat, cooking until the shrimp are pink, about 2-3 minutes. Stir in ½ cup of sliced mushrooms and cook for another 2 minutes, then deglaze the pan with ¼ cup of white wine. Season with salt and pepper.

Make the Béchamel Sauce: In a saucepan, melt 2 tablespoons of butter over medium heat. Once melted, whisk in 2 tablespoons of all-purpose flour to create a roux, cooking for 1-2 minutes. Gradually pour in 2 cups of milk, whisking continuously until the sauce thickens and is smooth, about 5-7 minutes. Season with salt, pepper, and freshly grated nutmeg, then stir in ½ cup of grated Parmesan cheese.

Assemble the Crepes: Lay a crepe flat on a clean surface and place a generous spoonful of the seafood filling in the center. Drizzle with a bit of the béchamel sauce and fold the crepe over the filling, then roll it up tightly. Place each assembled crepe seam-side down in a greased baking dish, repeating until all crepes are filled. Top with any remaining béchamel sauce.

Bake and Serve: Preheat your oven to 350°F (175°C). Bake the assembled crepes for 15-20 minutes or until heated through and the top is lightly golden. Once done, remove from the oven and let cool for a minute. Garnish with fresh parsley before serving.