Mix the mustard, vinegar, oil, mayonnaise, finely chopped chives and chopped parsley in a bowl to create a creamy sauce. Season with salt and pepper.
Peel the cervelats and cut them in half lengthways or whole into approx. 5 mm thick slices. Cut the cheese, spring onions and pickles into small cubes. Core the tomatoes and cut into cubes. Mix with the sauce and season to taste again.