– 1½ pounds of Russet or Yukon gold potatoes, [0.68 kg], peeled – 1 large carrot, boiled, peeled – 1¾ teaspoon of salt, (or more, to taste) – 3 egg (medium), hard-boiled, diced – 2 tablespoons of apple cider vinegar (or white wine vinegar) – 1 small red onion, minced – ¾ cup of sliced green beans, blanched, or the same amount of blanched peas – ⅓ cup of olive oil – 1 tablespoon of Dijon mustard, (optional) – 1 small apple, peeled and diced (see notes) – ¼ teaspoon of pepper (freshly-cracked, or ground), (or more, to taste)