Wash the potatoes, cook in boiling water for 20 minutes, quench. Leave to cool a little, peel and cut in half. Cut bacon into strips and fry until crispy in a pan. Peel and halve onions and cut them into strips.
Add onions to the bacon and deglaze with broth and vinegar. Season with mustard, salt and pepper and add it to the potatoes, let it soak well. Clean the celery (put celery green aside for garnishing), wash and cut into fine slices.
Blanch celery in boiling salted water, drain and add to salad. Season again and garnish with celery green.