4 pieces of desalted codfish1 lb (500 g) potatoes, sliced into rounds1 large onion, sliced into rings3 garlic cloves, minced1/4 cup olive oil1/2 cup green olives2 tbsp fresh parsley, choppedJuice of 1/2 lemonBlack pepper, to tasteSalt, if needed (adjust depending on the saltiness of the cod)