Heat (boil) water in a pot. Add the sausages and let them simmer for about 15 minutes (must not boil). In the meantime, clean and wash the rocket and let it drain in a sieve.
Clean, wash and cut the spring onions into rings. Clean the radishes (put a radish with a little green aside for garnishing), wash and cut into slices. Take the sausage out of the water, peel the skin and cut the sausage into slices.
Mix mustard and vinegar. Season to taste with salt, pepper and sugar. Fold in the oil. Mix sausage, radishes, spring onions, rocket and vinaigrette. Arrange on a plate garnished with radishes.
It goes well with farmhouse bread.