Wash and scrub the potatoes but leave their skins on.

Place them in a large saucepan, cover with lightly salted cold water and bring to the boil. Reduce the heat and simmer until the potatoes are tender when pierced with a knife.

Cooking time will depend on the size of the potatoes, but they should usually take around 20 to 25 minutes. Avoid overcooking them, as they need to remain firm enough to slice.

Cut the potatoes into slices approximately 5mm thick. Transfer the slices to a large glass or ceramic bowl.

Avoid using a reactive metal bowl because the acidic vinegar dressing may affect the flavour.

Add the beef stock, chopped spring onion, vinegar, salt, white pepper, sugar and mustard to a saucepan.

Stir everything together and bring the mixture just to the boil. Remove the pan from the heat as soon as it begins to bubble.

Pour the hot stock and onion mixture evenly over the warm potato slices.

Cover the bowl and leave the potatoes at room temperature for at least one hour. During this time, the potatoes will absorb much of the seasoned stock.

Pour over the sunflower or rapeseed oil and gently fold everything together. Take care not to break up the potato slices.

Taste and add more salt, pepper, vinegar or mustard when required.

Serve the potato salad at room temperature.

The flavour improves as it rests, so it can be prepared the day before and stored in the fridge. Remove it from the refrigerator around 30 minutes before serving.

Scatter some freshly sliced spring onions, or some chives to add colour.