Place the cubed Yukon Gold potatoes in a large pot and cover with cold water by at least 2 inches. Add 1 tablespoon of kosher salt. Bring to a boil over high heat, then reduce to a steady simmer and cook for 12–15 minutes, until the potatoes are just fork-tender but not falling apart. Test a few pieces — they should yield easily to a fork but still hold their shape.

Drain the potatoes in a colander and transfer them to a large mixing bowl. While still warm, drizzle with 1 tablespoon of the apple cider vinegar and a pinch of salt. Toss gently and let cool for 10–15 minutes. Do not fully cool before adding dressing — warm potatoes absorb flavor much better.

While the potatoes cook, place eggs in a small saucepan and cover with cold water. Bring to a full boil, then remove from heat, cover, and let sit for exactly 11 minutes. Transfer eggs to an ice bath and cool for 5 minutes. Peel and coarsely chop — you want distinct, chunky pieces.

In a medium bowl, whisk together the mayonnaise, yellow mustard, Dijon mustard, apple cider vinegar, sugar, salt, and black pepper until smooth and fully combined. Taste and adjust — it should be tangy, creamy, and slightly sweet with a sharp mustard bite.

Add the diced celery, red onion, and chopped pickles to the bowl of warm potatoes. Pour the dressing over the top and fold gently with a spatula until everything is evenly coated. Fold in the chopped hard-boiled eggs last, being careful not to break them up too much — you want visible chunks throughout.

Cover the bowl tightly with plastic wrap and refrigerate for at least 1 hour, preferably 2–4 hours or overnight. The salad will thicken and the flavors will deepen significantly as it chills.

Before serving, give the salad a gentle stir. If it looks a little dry after chilling, stir in a tablespoon or two of extra mayo and a small splash of vinegar. Transfer to a serving bowl, garnish with smoked paprika and fresh chives, and serve cold.