Place the diced potatoes in a large pot and cover with cold water by about an inch. Add 1 teaspoon of salt to the water.
Bring to a boil over medium-high heat, then reduce to a simmer. Cook until potatoes are fork-tender but still hold their shape, about 8-10 minutes.
Drain the potatoes thoroughly in a colander, then transfer to an ice bath for 1-2 minutes to stop cooking. Drain again and pat dry.
In a large mixing bowl, whisk together the Greek yogurt, Dijon mustard, apple cider vinegar, olive oil, dill, salt, and pepper until smooth.
Add the slightly cooled potatoes to the dressing while they're still somewhat warm. Gently fold the potatoes into the dressing using a rubber spatula.
Fold in the sliced green onions and any optional ingredients you've chosen.
Cover and refrigerate for at least 30 minutes (or up to 4 hours) to allow the flavors to meld.
Before serving, gently stir the salad and taste for seasoning. Adjust if needed.
Transfer to a serving bowl and garnish with extra herbs, a sprinkle of paprika, and a few slices of green onion if desired.
