Peel the potatoes, cut them into small bite-size pieces of roughly equal size (a medium-large potato is usually cut into about 10-12 'cubes'). Rinse in cold water to remove any excess starch, then place them in a pan with enough lightly-salted water to completely cover them. Bring the water to the boil and cook for just 10-12 minutes. when you think the potatoes are near being cooked, pierce one or two pieces gently with a fork. If the fork goes in easily, they are cooked. Do not be tempted to overcook them as you want them to remain whole. Remove from the heat, drain off the water and allow the potatoes to cool for 5-10 minutes so they remain warm but not hot.
Meanwhile, make a Vinegar Dressing. Peel and finely chop the shallot (if you prefer, you can use thinly sliced spring onion [a.k.a. scallions or salad onions]) and stir in to the Vinegar Dressing. When the potatoes are luke warm, add the dressing mixture and stir gently with a wooden spoon. Sprinkle with chopped parsley and eat while still warm.