Insalata di Cipolle e Fagioli

1 pound dried cannellini beans (white kidney beans) or other beans such as Great Northern or navy
2 tablespoons salt
2 medium white onions (red or yellow onions may be substituted, but yellow will make the salad rather sweet), chopped
1/4 cup chopped Italian parsley
1 cup extra-virgin olive oil
salt and freshly ground pepper to taste

1 tablespoon or more balsamic or other vinegar to taste (optional)

Put dried beans in a pot, cover with two inches of water, and soak overnight. Add 1 quart of water and salt and simmer, uncovered, until beans are tender, about 1 1/2 hours. Check water level periodically to be sure they do not boil dry.

Drain beans and rinse in cold water for 5 minutes to cool (or refrigerate). Toss with chopped onion, parsley, and olive oil. Season with salt, pepper, and vinegar. Serve cool or cold. Serves 6.