Put the cod in a deep dish, add cold water to cover, and let it soak for 2 days in the refrigerator in order for it to "plump" up and change the water several times. Rinse and dry the fish and cut it into 5 cm chunks. Dredge the fish in the flour, shaking off the excess. In a large skillet, heat 2 Tbl of the butter and the olive oil. Add the fish pieces and brown them well on all sides over medium-high heat. Sprinkle the fish with the minced garlic and parsley and stir the mixture gently. Cut the remaining 2 Tbl butter into bits and add it to the pan. Sprinkle the fish with salt and pepper and pour over the lemon juice. Serve immediately.