Nigel's recipe suggested using creme fraiche instead of the usual mayonnaise, which seemed a bit too rich and creamy to me, so I did half-and-half, using Hellmann's and half-fat creme fraiche instead. It needs a bit of poke, with Dijon and grain mustard, lemon juice and salt and pepper. It was very good, although next time I'll cut the celeriac even finer (I don't have a mandolin grater) to avoid having to chew QUITE so much! I served it with smokey applewood ham and lots of watercress for a healthy salad. We started with vegetable and barley broth to get some warmth into us!