Mix 3 tablespoons of vinegar and 1/2 litre of water. Wash and peel the black salsifies, cut them into pieces and put them into the vinegar water. Cook in boiling salted water with remaining vinegar for about 30 minutes.
Boil the eggs in boiling water for about 9 minutes until hard, drain them, rinse with cold water, peel and halve them. Heat the fat in a pot, add flour, sweat it on and deglaze with broth and cream. Bring to the boil, stir in mustard and season to taste with salt, pepper and sugar.
Wash the chervil, dab dry and pluck the leaves from the stems. Roast the mustard seeds in a dry pan for about 2 minutes. Drain the black salsifies on a sieve. Dice the ham. Add eggs, black salsify and ham to the sauce and simmer again for another 5 minutes while stirring.
Serve egg ragout sprinkled with mustard seeds and chervil in a bowl. Boiled potatoes taste good with it.