1. Wash the potatoes and cook them for 30 minutes in salted boiling water.
2. Place the egg in simmering water for 10 minutes.
3. In another pot of boiling water, poach the cervelat sausage for 10 minutes.
4. Peel and finely chop the shallot.
5. Cut the pickles into small pieces and chop the parsley.
6. Cut the potatoes, egg, and cervelat sausage.
7. Place them in a salad bowl, adding the pickles and parsley.
8. In a small bowl, prepare the dressing by mixing mustard, vinegar, oil, salt, and pepper.
9. Pour the dressing over your salad just before serving.