Peel the potatoes and cut them into 1/2 inch cubes. Put them in the Instant Pot with 1 cup of water and set them for 4 minutes. Use the Instant Release method. Remove them from the pot and drain them set aside.
Use a knife to remove the strings from the celery. Then slice the celery into 1/8 inch slices. Set aside.
Chop the onion and set that aside.
Chop the Italian parsley as well and keep a few sprigs out for decoration. Set aside.
*** Make the Dressing ***
Combine the mayonnaise with the mustard, white pepper, and justice. Whisk together and taste for seasoning. Add the pickle juice a little at a time until the dressing is a tiny bit thinner, but not so thin that you can pour it.
When the dressing is made, put the potatoes and vegetables in a large bowl and pour the dressing overall. Use a large spoon to mix it all together. Put it in the refrigerator to cool.
At serving time, carefully put the salad into a nice serving bowl and garnish it with a few sprigs of celery. Enjoy!
If you don't like red onions, you can use white onions. Red onions are nice because they have a mild flavor and offer a pop of color. If you cannot find Italian or flat-leaf parsley, you can use curly parsley instead.