In a medium saucepan, over medium heat, melt the butter. Stir in the flour and cook for 2 minutes. Whisk in the milk, 1/2 cup at a time. Season with salt, pepper and nutmeg and cook, stirring constantly for 4 to 6 minutes. Remove from the heat and stir in the spinach and 1/2 cup of the Parmesan. Set aside.
In a mixing bowl, combine the ricotta cheese, egg, garlic and mozzarella cheese. Season with salt and pepper. Mix well. Set aside.
Grease an 8 by 8 by 2-inch square pan. To assemble, spread 1 cup of the sauce over the bottom of the pan. Season the crabmeat and lobster with salt and pepper. Sprinkle 1/4 of the crabmeat and lobster over the sauce. Sprinkle some of the remaining Parmesan over the crabmeat. Cover the cheese with a sheet of the fresh pasta. Spread 1/4 of the cheese filling evenly over the pasta. Repeat the layering until all of the ingredients are used. Top the lasagna with the remaining cup of the sauce. Place in the oven and bake until bubbly and golden, about 45 minutes.
Remove from the oven and cool for 10 minutes before serving. Drizzle lightly with truffle oil, if desired.