Begin by preparing your béchamel sauce.

Add the butter to a medium saucepan and melt. Then, while stirring with a whisk, add in the flour. Whisk until blended. Slowly add the milk while whisking. Add salt and pepper to taste. Lower the heat and stir until thick and smooth: about five to seven minutes. Remove from the heat and set aside.

In a large skillet, melt 1 tablespoon of butter. Add in the onions and garlic and cook for about one minute. Then, add in the shrimp, scallops, and flounder. Sprinkle with salt and pepper.

When the shrimp begins to turn pink, add the wine. Cook just until the wine comes to a boil, then turn off the heat.

Transfer the seafood to a bowl using a slotted spoon leaving any liquid in the skillet.

Bring the leftover liquid to a simmer, then add in the sliced mushrooms and cook for about five minutes.

Add in the béchamel sauce and stir to combine.

Add tomatoes, then simmer for about five to six minutes.

Add in the cream, red pepper flakes, parsley, oregano, basil, and salt and pepper to taste. Stir to combine.

Finally, to the sauce, pour in any liquid that may have accumulated in the bowl of your reserved seafood. Stir to combine and then remove from the heat.

Preheat oven to 375 degrees F.

Butter the bottom and sides of a 9×13 casserole dish.

Spoon a layer of sauce over the bottom, then add about one-third of the seafood mixture. Cover with more sauce, then layer with three cooked lasagna strips.

Add another layer of seafood, then top with a thin layer of sauce. Sprinkle with one-fourth cup swiss cheese and one-fourth cup parmesan cheese. Cover with three more lasagna noodles.

Scatter the remaining seafood on top, then add another light layer of sauce. Cover with the remaining three lasagna noodles. Then spoon the remaining sauce over the top.

Sprinkle the top with the remaining swiss and parmesan cheeses.

Bake for 40 to 50 minutes, or until hot and bubbly.