Rinse beans and soak overnight in plenty of water. The next day, drain the water, pour the beans in a bowl, add fresh water, bring to a boil, remove the foam, add the bay leaf and cook for 40 minutes over low heat. Tilt in a colander and cool. Put the beans in a bowl, add vinegar, olive oil, salt, pepper and sugar, stir and let stand for 1 hour. Add green onions, tomatoes, chopped herbs, salt and pepper and serve, garnish with sprigs of parsley and mint.