Pour the beans into a sieve, rinse and drain. Peel and chop the onions. Cut ham into strips. Mix beans, onions and ham.
Whisk vinegar with 2 tablespoons of water, salt, pepper and sugar. Beat down the oil in a thin stream. Mix the vinaigrette with the bean salad and season to taste with salt and pepper. Wash the chives, dab dry and cut into small rolls, sprinkle over the salad.
Served with farmhouse bread with Lyoner, Black Forest ham, canned blood and liver sausage with mustard and onion rings, gherkins and cream cheese with herb oil.