Clean and prepare the fish before cooking the pasta.
Clean and wash the mullet well. Remove the heads and fishbones of the sardines, then cut into small pieces.
In a large saucepan, sauté the onion until golden brown in oil with the pressed garlic and sardines. Add the tomato sauce, a pinch of thyme, salt, and hot pepper. Cook for a few minutes.
Add the mullet to the sauce and cook for the minimum amount of time necessary (at most 2 minutes). Once cooked, remove the mullet from the sauce and set aside, making sure to keep it warm.
Finely chop the parsley and add to the sauce.
Cook the bucatini pasta. When cooked al dente, drain and toss it in the pan with the sauce.