Béchamel Sauce:

• 4 tablespoons unsalted butter
• 4 tablespoons all-purpose flour
• 2 cups milk
• Salt and freshly ground pepper, to taste

Seafood Mixture:

• 1 tablespoon unsalted butter
• 1 tablespoon finely chopped onion
• 1 garlic clove, minced
• 3/4 lb boneless flounder fillets, cut into bite-sized pieces
• 1 pound raw shrimp, peeled and deveined
• 1 pound scallops
• Salt and freshly ground pepper, to taste
• 1/2 cup dry white wine
• 2 cups thinly sliced mushrooms
• 1 cup crushed canned tomatoes
• 3/4 cup heavy cream
• 1/4 teaspoon red pepper flakes
• 3 tablespoons finely chopped fresh parsley
• 1/4 teaspoon dried oregano
• 1/4 teaspoon dried basil
• 9 lasagna noodles, cooked according to package directions
• 1 cup grated Swiss cheese
• 1/2 cup shredded Parmesan cheese