While the potatoes cook (next step), prep all your fresh ingredients to streamline assembly. Finely dice the red onion and set aside. Chop the fresh dill and chives, keeping them separate so their delicate flavors stay bright. Drain the capers well and roughly chop the pickles—I like to keep them in slightly larger pieces so you get that satisfying crunch throughout the salad. Having everything prepped and ready makes the final assembly quick and ensures even distribution of flavors.
Bring a large pot of salted water to a boil and add the whole potatoes. Simmer for 15-20 minutes until just fork-tender—don't overcook or they'll fall apart when mixed. Drain well and let cool slightly until you can handle them comfortably. Peel the warm potatoes (the skin comes off much easier when they're warm) and cut into bite-sized cubes or thin slices, about ½-inch pieces. Transfer to a large mixing bowl.
In a small bowl, whisk together the mayonnaise, mustard, and apple cider vinegar until smooth and well combined. Add the sugar, a pinch of salt, and several grinds of fresh pepper. Taste and adjust the seasoning—the vinegar should be noticeable but balanced by the mayo's richness. I prefer Hellmann's mayo for its creamiest texture, which helps create that luxurious coating on every potato piece.
Pour the creamy dressing from Step 3 over the warm potatoes and gently fold it in, making sure every piece gets coated. The warm potatoes will absorb the dressing beautifully, creating a cohesive, flavorful salad. Now add the prepared mise en place from Step 1—the red onion, capers, pickles, dill, and chives—folding gently until everything is evenly distributed. Taste and adjust seasoning with a bit more salt and pepper if needed.
Transfer the potato salad to a serving dish and refrigerate for at least 1 hour before serving. This resting time allows the flavors to meld together and the salad to firm up to the perfect texture. You can make this up to a day ahead—just store it covered in the refrigerator. Give it a gentle stir and taste again before serving, adding a splash more vinegar or a pinch of salt if desired.