Leave the dried cod in water for at least 3 or 4 nights (leave it more during winter).
Once the cod is ready, gently cook the onions in a pan with 1 glass full of olive oil, until golden brown. Add the anchovies and turn off the heat.
Add, only off the fire, the chopped parsley.
Chop the cod in large chunks, dust them with flour, remove the eccess flour and place them in a tray. pour over the cod the onion mixture, milk, parmisan, salt and pepper and put enough extra virgin olive oil to cover all the ingredients,
Cook in a oven (middle heat: i.e. 160 degrees) for at least 4 hours without stirring or mixing.