Finely chop the green onion into very small cubes and place it on a plate with a little vinegar.

Boil the potatoes, let them cool, then cut them into cubes.

Squeeze the onion to remove excess vinegar and add it to the potatoes.

Add a little dill and a little parsley.

Mix the mayonnaise, mustard, and lemon juice in a food processor, then pour the sauce over the potatoes.

Stir to coat the potatoes evenly with the sauce.