Step 1: Prepare the béchamel sauce

• In a medium saucepan, melt the butter over medium heat. Add the flour and whisk continuously for 1–2 minutes until golden.
• Gradually whisk in the warmed milk, ensuring there are no lumps. Cook for 5–7 minutes, stirring frequently, until the sauce thickens.
• Season with garlic powder, nutmeg, salt, and pepper. Set aside.

Step 2: Cook the seafood

• Heat a skillet over medium heat and lightly sauté the shrimp and scallops for 2–3 minutes until just cooked. Remove from heat and set aside.

Step 3: Prepare the cheese mixture

• In a large bowl, combine the ricotta cheese, 1/2 cup of Parmesan cheese, and 1 cup of mozzarella cheese. Mix until smooth.

Step 4: Assemble the lasagna

• Preheat your oven to 375°F (190°C).
• Spread a thin layer of béchamel sauce at the bottom of a greased 9×13-inch baking dish.
• Place a layer of lasagna noodles over the sauce. Spread a portion of the ricotta mixture, sautéed seafood, spinach, and béchamel sauce over the noodles.
• Repeat the layers, finishing with a layer of béchamel sauce. Top with the remaining mozzarella and Parmesan cheese.

Step 5: Bake the lasagna

• Cover the dish with foil and bake for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the top is golden and bubbly.

Step 6: Rest and serve

• Allow the lasagna to rest for 10 minutes before slicing and serving.