We will start by preparing the filling. For that we chop the onion and sauté for 20 minutes in the oil over low heat, it should be soft and transparent. While in a saucepan with water, we boil the desalted fish as explained here and let it cook for three minutes, drain it and separate it into flakes.
When the onion is poached, add the cod and the raisins and let everything cook together for another four minutes. We drain the oil and let it cool, reserving this cold oil leftover for the dough.
For the dough, in a bowl we add the flour, mix the salt with the milk and add. Add the oil from the sauce and a lightly beaten egg. We are forming a ball with our hands, once achieved we cover it with a cloth and let rest 15 minutes before using it.
Once the time has passed, we divide the dough in half, leaving one part slightly smaller than the other. We roll out the largest portion of dough between two round baking papers, we place it on top of a mold or on a baking tray with the paper.
We stretch the other part in the same way, leaving it a little smaller than the base. We spread the filling on top of it, cover with the other part of the dough on top and we tuck in the base making a closed cord with our fingers to prevent the filling from coming out.
With scissors we cut a kind of chimney, so that the empanada breathes and does not burst and with the dough cuts we make some decorations. We paint with beaten egg and a pinch of salt, and we bake in the oven preheated to 190 degrees for 45 minutes or until we see it golden. Remove from the oven and paint it hot with the remaining oil from the sauce.