Fill a large pot with water and bring it to a rolling boil over high heat. Place unpeeled potatoes into the water—don't cut them beforehand because they'll absorb too much water and fall apart. I learned this the hard way after my first attempt turned into mashed potato soup. Boil until a fork slides through the thickest part with almost no resistance, about 20 minutes depending on size.

While potatoes cook, peel and roughly chop the hard-boiled eggs and set them aside in a small bowl. This step takes just three minutes and saves you time later when you're assembling everything. I prep the eggs while standing at the counter because it keeps me from pacing anxiously while waiting.

Drain the potatoes in a colander and rinse them briefly under cool water—just enough to stop the cooking but not so much that you wash away starches. Let them sit for five minutes until cool enough to handle. The potatoes should still be slightly warm because warm potatoes absorb dressing better than cold ones, which is why texture matters here.

Cut the cooled potatoes into 3/4-inch cubes and transfer them to a large mixing bowl. Don't peel them—the skins add texture and nutrients that belong in this dish. A sharp knife makes this step faster; I use my 8-inch chef's knife because it handles the size perfectly without slipping.

Add mayonnaise, Dijon mustard, salt, and sugar to the bowl with potatoes. Fold everything together gently using a rubber spatula—don't stir aggressively because you'll mash the potatoes and end up with a gluey texture. This is the moment where most people rush, but taking 30 seconds to be intentional makes the difference between good and excellent.

Fold in the diced red onion, celery, and sweet pickle relish until everything is evenly distributed. The relish juice adds sweetness that balances the Dijon's sharp edge. Taste the mixture and add more salt and pepper if needed—trust your palate here, not the recipe.

Add the chopped eggs and fresh parsley, then drizzle the lemon juice over everything. Fold gently one final time. Lemon juice prevents oxidation and adds brightness that makes people ask what the secret ingredient is. The answer is always the thing you almost skipped.