Dressing: Shake in a jar.

Halve so they are about 2.5cm / 1" pieces (cut large ones into 3).

Bring 4 litres / 4 quarts water to the boil, add salt. Add potatoes, bring back up to the boil then reduce to simmer. Cook for 5 minutes or until just cooked - don't let them overcook or become too soft, they will keep cooking from residual heat.

Drain and immediately transfer to a bowl.

While potatoes are hot, pour over half the Dressing. Use rubber spatular to gently stir.

Set aside to marinate for at least 30 minutes, even overnight.

Add green onions and parsley, pour over remaining Dressing. Carefully toss with rubber spatular, then serve. Great warm or at room temperature, and it's also great the next day.