Prepare the pasta dough according to the recipe and roll out to the thinnest setting on a pasta rolling machine. Cut the sheets into 1/4-inch thick strips, dust with semolina flour and set aside, covered with a damp kitchen towel, until ready to use.
In a 12 to 14-inch saute pan, combine the wine, onion, bay leaves, and a pinch of salt and pepper and cook over high heat until the wine boils. Add the sole and shrimp. Reduce to a simmer and cook for 5 minutes. Strain out the solids, reserving them, and return the liquid to the pan. Add the milk and bring to a simmer.
Once the fish and shrimp are cool enough to handle, cut the shrimp into 3 pieces each and the fish into strips. Set aside.
In a heavy-bottomed saucepan, heat half of the butter until it is melted. Add the flour and whisk it in for 30 seconds. Remove the saucepan from the heat and whisk in the milk and wine mixture. Return the pan to the heat and bring to a boil over low heat. Cook over low heat for 15 to 20 minutes. Mix in the parsley and bread crumbs and season with salt and pepper, to taste. Remove from heat and set aside.
Bring 6 quarts of water to a boil and add 2 tablespoons salt. Cook the tagliatelle in the boiling water until tender yet al dente, about 2 minutes. Drain the pasta and, in a large bowl, dress it with 1/3 of the fish sauce.
In a shallow casserole that has been greased with a little of the remaining butter, place half the dressed pasta, and top it with the cooked fish and shrimp. Spoon a little bit of the sauce over the seafood and top with the remaining pasta. Cover the top with the remaining pasta. Melt the remaining butter in a small pan on the stovetop and pour it over the top of the casserole. Bake for 20 minutes, then let rest for 5 minutes before serving.
As you expand the well, keep pushing the flour up from the base of the mound to retain the well shape. The dough will come together when half of the flour is incorporated.
Start kneading the dough with both hands, using the palms of your hands. Once you have a cohesive mass, remove the dough from the board and scrape up and discard any leftover bits. Lightly reflour the board and continue kneading for 6 more minutes. The dough should be elastic and a little sticky. Wrap the dough in plastic and allow to rest for 30 minutes at room temperature.
Roll the pasta out on a pasta rolling machine to the desired thickness.