Preheat your oven to 350°F and grease a 9 x 13-inch baking dish. Set it aside.

To make the bechamel sauce, melt the butter in a saucepot over medium heat. Add the flour and cook for one minute. Gradually add the milk, stirring continuously until the sauce thickens. Stir in the parmesan cheese, then remove from heat.

In a bowl, prepare the cheese filling by combining ricotta cheese, whisked egg, shredded mozzarella, dried parsley, and salt. Stir until well mixed and set aside.

Heat olive oil in a skillet. Add the seafood mix along with salt, pepper, and parsley. Cook for about 3 minutes until the seafood is just cooked through.

To assemble the lasagna, spread a thin layer of bechamel sauce on the bottom of the prepared baking dish. Place lasagna sheets over the sauce. Spread 1/3 of the ricotta mixture over the lasagna sheets, followed by 1/3 of the seafood mix, and 1/3 of the bechamel sauce. Repeat these layers two more times, finishing with a layer of shredded mozzarella and freshly grated parmesan on top.

Bake the lasagna for 35 minutes. If the top browns too quickly, cover with tin foil and continue baking until the cheese is melted and bubbly.

Remove the lasagna from the oven and let it cool for a few minutes before slicing and serving.