Cut the potatoes into 2.5-3cm chunks
(step 1), so that they are all the same size
and will cook evenly. Put them in a pan of
boiling water. Once the water has returned
to the boil, lower the heat slightly and
cook for about 10 mins or until just cooked
and still keeping their shape. Tip them
into a colander to drain well, then transfer
to a large bowl.
While the potatoes are cooking, mix
together the mayonnaise, yogurt, crème
fraîche, mustard and milk. Add the spring
onions, then most of the chives and
tarragon to the potatoes (step 2). Season
with pepper and a pinch of salt.
Spoon the dressing over the potatoes
while they are still warm (step 3), then toss
gently together so that they are well
coated but don’t break up. Tip the potato
salad into a serving bowl and scatter over
the remaining chives and tarragon. Serve
cold – but the flavour is best if not served
straight from the fridge.