Cut the potatoes into small, uniform cubes. Put them in a large saucepan with two litres water, two teaspoons salt and two teaspoons herb butter (you can use plain butter if you like). Boil until just tender - because the potatoes are already diced this will happen quickly.
To make the dressing, combine the yoghurt and mayonnaise in a bowl. Add a little milk and mix until it is nice and smooth, not too thick. Season to taste with salt, pepper and sugar if desired.
Mix the potatoes, cucumber and dressing in a salad bowl. If adding pork, fry the cubes in a little butter first and let cool. Chill 2 hours before serving and sprinkle with chives.