Boil the potatoes in their skins, peel and dice them.

Bring vinegar water (clearly sour) to the boil with salt, pepper, bay leaves, juniper, cloves, mustard seeds if using, and halved onions, then pour it over the potatoes.

Leave in the fridge overnight and drain in the morning.

Thin the mayonnaise with yoghurt and fold it in.

Add the apples.