For the mayonnaise: Your egg yolk should be room temperature. Put it with a bit salt and pepper as well as the lemon juice in a bowl. Mix for 1 min with your mixer.
Now the oil has to be added very carefully by pouring it in slowly (fine stream) while mixing the mass with the handmixer or kitchen machine. This way the oil mingles well with the egg yolk. Note: It is very very important to add the oil as slowly as possible in a very fine stream. If you pay attention to that, the mayonnaise is actually quite simple to make. Add the yogurt and mustard, mix and season your mayonnaise. The mayonnaise is now ready and can be processed further.
First boil the potatoes as jacket potatoes with a little salt, drain and peel. Let them cool down and cut into small pieces and put them in a big bowl. (Optimal you cook the potatoes one day before use and let them cool with skin over night.) Boil the broth and cook the chopped onion in it for about 3 minutes. Take off the stove.
Add mustard, the eggs if you have, vinegar and onion mixture to the potato pieces and let it steep a little. Cut the pickles and parsley small add them, mayonnaise and the pickles' water and stir carefully. Last season with mayonnaise. Now you can enjoy your potatoe salad...