Make the White Bechamel Sauce: In a medium saucepan over medium heat, melt the butter completely. Add minced garlic and sauté for 1 minute until fragrant, being careful not to let it brown. Gradually whisk in the flour to form a smooth roux. Cook for 1–2 minutes. Slowly pour in the warm milk while whisking constantly until the sauce thickens into a creamy consistency. Stir in salt, pepper, and nutmeg. Remove from heat and set aside.

Cook the Seafood: In a large skillet over medium heat, melt 1 tablespoon of butter. Add the shrimp and cook for 2–3 minutes until pink and just cooked through. Remove and set aside. In the same skillet, gently warm the crab meat for 1–2 minutes, being careful not to break it apart. Set aside with the shrimp.

Prepare the Pasta: Bring a large pot of salted water to a boil. Add the lasagna noodles and cook until al dente according to the package instructions. Drain and lay them flat on a clean kitchen towel to prevent sticking.

Assemble the Lasagna: Preheat the oven to 180°C (350°F). In a large baking dish, spread a thin layer of bechamel sauce on the bottom. Arrange lasagna noodles slightly overlapping. Spread a portion of ricotta evenly, sprinkle with mozzarella and Parmesan, then add a mix of shrimp and crab meat. Drizzle with more bechamel sauce. Repeat the layers until all ingredients are used, ending with a generous topping of mozzarella and Parmesan.

Bake to Perfection: Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 15–20 minutes, or until the top is golden and bubbling. Let the lasagna rest for 10 minutes before slicing to allow the layers to set.