Gently fry the garlic and onion in the olive oil, add 1glass of dry white wine and allow it to bubble fiercely for a few minutes. Reduce the heat, add the tomato coulis and the tomato purée and stir in well. Bring the sauce to the boil and add the baccalà cut roughly into 2cm/1in squares. Reduce the heat and let the sauce gently simmer for 1 hour. Season with the anchovies and a generous sprinkling of black pepper.
Serve this sauce with either soft polenta or tagliatelle. Sprinkle finely chopped parsley on top. Scraps of baccalà can be used for this dish.