Halve or quarter the potatoes, depending on size, and place in a saucepan. Cover with water and add a generous pinch of salt. Bring to the boil and cook for 12-15 minutes until tender. Drain well and leave to cool.
Put the cold potatoes in a bowl and mix in the spring onions and chives. Blend the mayonnaise and vinegar and toss into the potatoes. Cover and chill until required.
Just before serving, heat a frying pan until hot and stir fry the bacon lardons for 4-5 minutes until cooked through and crispy. Drain well. Toss half into the potato salad and transfer to a serving bowl.
Sprinkle over the remaining lardons and serve immediately. Delicious with barbecued pork chops and sausages.