Peel the potatoes and cook for about 20 minutes, drain the water and let the potatoes cool down.
Cut the cooled potatoes into slices (can be done very quickly with an egg cutter).
Peel and slice the onions. Clean the beans, wash them (if they are fresh) and cook in salted boiling water for 10 minutes, rinse and drain.
For the vinaigrette:
Mix the vinegar, salt, pepper and salad herbs together. Beat in the olive oil.
Mix the potatoes, beans and onions and pour the vinaigrette over them. The salad can be served with whole matjes or cut the fillets into small pieces and mix with the salad.