Step 1 - Soak the beans in cold water for 8 to 12 hours. After this time, discard the water and cook them in a pot in plenty of water with a little salt, until they are soft but firm. Reserve the cooking water.
Step 2 - Separately, cut the onion into cubes, add a tablespoon of sugar, dampen with your hand and rinse with cold water. Drain and set aside.
Step 3 - To assemble the salad, strain the beans and put them in a bowl with the reserved onion and chopped parsley.
Step 4 - Season with salt, lemon juice or vinegar and finally the oil.
Step 5 - Mix well all the ingredients. Add salt and pour into a bowl.