Slice potatoes into 1/4” slices, add to a pot of salted water and bring to a boil. Reduce heat to medium high (simmering) and let cook for 10-13 mins, until fork tender.
Strain and add to a large bowl. While still warm, Pour dill pickle juice over potatoes and add 1/4 of the boiled potatoes to a separate small bowl. Mash small bowl of potatoes with a potato masher and set aside.
Prepare dressing by combing all ingredients into a small bowl and whisking to combine.
Slice the scallions, mince the onion, shave the sweet corn off the cob & chop the fresh dill. Add to the bowl of potatoes, and return small bowl of now mashed potatoes to the bowl — drizzle with dressing. Toss to coat and season with salt and pepper to taste.