Soak the dried peas in two liters of water overnight.
Put on the next day with the soaking water and simmer on a low flame for two hours.
Clean and finely chop the onions, celery and leeks, peel and dice the potatoes and add everything to the peas. Top up with the broth as required and let everything cook for about 15 minutes.
In the meantime, fry the bacon until crispy.
Finely chop the herbs and cut the sausages into not too thin slices. Add to the soup. Season everything with salt, pepper and mustard and bring to the boil again briefly.