To make the tomato sauce: Preheat oven to 475 degrees F.
Cut the tomatoes into wedges and put in a small bowl. Add the oil and balsamic vinegar, and then season with the salt and pepper.
Place the tomatoes on a rack, and then place the rack on a sheet pan. Roast for 30 to 45 minutes until the edges brown well and the tomatoes become very soft.
Put the tomatoes and all juices in a sieve and drain over a small pot. This should remove the skin and seeds and leave you with a thin tomato sauce. Bring the sauce to a simmer and reduce until the sauce is a medium thickness, about 5 minutes. Stir in the butter. Add the salt and pepper, to taste, and keep warm.
To make the stuffing: In a large saute pan, add the olive oil, then chorizo, and let it cook for about 2 minutes. Add the onion and garlic, and saute on medium heat until the onions are soft, about 2 or 3 minutes. Add the oregano and bay leaf and cook another 2 minutes, until you can smell the herbs cooking. Add the diced bell peppers and sherry and let simmer 1 minute. Turn off heat. Fold in the bread crumbs until all liquid has been absorbed. Season with salt and pepper, to taste, and set aside.
To make the potato crust: Using an Asian turning mandoline or a vegetable peeler, peel long thin strings of potato. Put the potato strings in a small bowl. Season with salt and pepper and add the cornstarch. Mix with a spoon until well blended and set aside.
To stuff and crust the fish: Preheat oven to 375 degrees F.
Lay out the fillets flat on a work surface and season with salt and pepper. Place a golf-ball sized piece of stuffing in the center of 1 fillet. Lay another fillet over the stuffing and press softly to distribute the stuffing. Take a small handful of the stringed potato mixture and lay it over the top fillet, leaving only 1/4-inch uncovered around the edges. Press down lightly. Repeat process with remaining fillets.
Heat a large nonstick, oven-proof saute pan and melt the butter. Place the flounder in the pan, potato-side down, and fry until golden brown, about 5 minutes. Carefully flip over stuffed flounder and place pan in oven for 9 to 12 minutes, or until fish is cooked through.
Remove the fish from the oven. Ladle 2 ounces of tomato sauce onto the plate. Lay the stuffed flounder over the sauce and serve with a vegetable, such as sauteed spinach.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.