Preheat the oven to 375 degrees F. Grease a sheet pan with olive oil. Butter 4 to 6 ramekins or a casserole dish. Set aside.
For the noodles: Put a pot of salted water on to boil. Drop in 6 to 8 lasagna noodles, taking care not to break them. Cook to al dente according to package directions. Do not overcook. Remove the noodles to the greased sheet pan one at a time. The olive oil will keep the noodles from sticking. If you are using ramekins or molds, cut the cooked noodles to a size that will fit with a circle cutter. If you are using a casserole dish, you can cut the noodles to the correct size with a knife or kitchen shears.
For the sauce: Put the milk in a saucepan over medium heat and bring just before boiling. Remove from the heat.
In a large skillet or saucepan, sweat the onions in 3 tablespoons of the butter. Do not allow to brown. Add the flour to form a paste. Cook until a pale blonde color, 3 to 4 minutes. Add the scalded but cooled milk to the roux a little at a time, whisking to keep from clumping. Add the seafood stock, whisking it in a little at a time. Cook for 15 to 20 minutes over medium-low heat, stirring almost constantly and scraping the bottom to prevent scorching. Reduce the heat to low. Add the Parmesan. Add more seafood stock if the sauce is too thick, whisking in a little at a time. Remove from the heat. Stir in the lemon juice, thyme, salt, white pepper, nutmeg, canned white tuna and peas.
For the topping: Put the breadcrumbs, 1/2 cup Parmesan, butter, parsley and salt and pepper to taste into the bowl of a food processor and pulse to combine well.
To assemble: Layer lasagna style, alternating the noodles, sauce and tuna belly fillets, ending with a bit of the sauce on top. Add the topping, making sure to get the topping all the way to the edges of the container.
Place the ramekins or casserole on a baking sheet. Bake until golden brown on top, about 35 minutes.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.