Place the black-eyed peas in cold water and boil them for 5 minutes. Drain them and discard the water. Place them in clear water and boil them for further 20 minutes. Season them with salt while cooking. Drain them and leave them to come to room temperature. Place them in a salad bowl and add the spring onions, peppers and onion rings. Whisk the olive oil with the vinegar, salt and pepper until you get a dressing with a creamy consistency. Pour the dressing over the salad and sprinkle with lots of parsley. Give everything a good toss to combine all the ingredients well and serve.