Make the béchamel sauce: Melt 3 1/2 tablespoons butter (50 g) in a small saucepan. Add 2 tablespoons flour, a pinch of salt, and slowly whisk in 2 cups warm milk (500 ml). Cook in a double boiler, stirring constantly, until it reaches the desired consistency.
Alternatively, you can use store-bought béchamel sauce.

Clean the mussels and cook them in a large pot until they open. Remove the mussels from their shells.

Rinse the clams and cook them in a pot until they open. Remove the clams from their shells.

Clean and peel the shrimp, then boil them in salted water for 2 minutes.

In a skillet, sauté garlic and cilantro (parsley), then add the mussels, clams, and shrimp. Cook for 2 minutes to blend the flavors. Add salt to taste at the end.

Add the seafood to the béchamel sauce.

Layer the lasagna by alternating béchamel sauce and pasta sheets.

Add a little milk before baking to keep the lasagna from drying out.

Bake in a preheated oven at 365°F (185°C) for 15 minutes.

You can use any type of fish you like. For example, I added some sea bass.