2) Meanwhile add the sour cream to a bowl with the whole-grain mustard, salt, white pepper and chopped chives, reserving a teaspoon of chives to sprinkle on top. Stir all the ingredients together.
3) Scatter the remaining chives over the top of the sour cream mix. If you are not eating it straight away, store it covered in cling film in the refrigerator.
4) When the potatoes are ready with a crisp skin and soft inside, remove them from the oven, take them off the skewers and cut a cross in the top of each. Slightly squeeze each one so it opens out and place into a bowl.
5) Serve the potatoes hot with the chive sour cream on the side so people can help themselves.