Mix flour, salt, and pepper together on a large plate.
Drop flattened chicken breasts in flour mixture. Set aside.
Boil water, cook linguine aldente.
Heat olive oil and butter together in a large pan. When butter is melted and oil/butter mixture is hot, fry chicken breasts until nice and golden brown on each side. Remove from pan and keep warm.
Without cleaning the pan, add onions and garlic and gently stir for 2 minutes. Pour in wine and scrape the bottom of the pan, getting all the burnt flavorful build up off the bottom. Allow wine to cook down until reduced by half, about 2 minutes.
Pour in crushed tomatoes and stir to combine. Add sugar and more salt and pepper to taste. Allow to cook for 30 minutes. Toward the end of cooking time, add chopped parsley and give sauce a final stir.
Carefully lay chicken breasts on top of the sauce and completely cover them in grated Parmesan. Place the lid on the pan and reduce heat to low. Allow to simmer until cheese is melted and chicken is thoroughly heated. Add more cheese to taste.
Place cooked noodles on a plate and cover with sauce. Place chicken breast on top and sprinkle with more parsley. Serve immediately.