I am allergic to mustard so am asking for a possible alternative ingredient? In general and specifically in Nigella’s recipe for the Buttermilk Dressing for the New Potato, Asparagus And Radish Salad.
Nigella uses mustard to add piquancy, and sometimes extra heat, to different dishes. Unfortunately it would be difficult to recommend a universal substitute for mustard in all of the recipes, as it depends on the individual recipe. Where heat is needed then a chilli or hot sauce could be an alternative. In many cases the mustard can just be omitted.
Nigella's Asparagus, Radish And New Potato Salad has a buttermilk dressing made with buttermilk, mustard, lemon juice and herbs. For this dressing either horseradish or wasabi would be possible alternatives. However both of these tend to be hotter than Dijon mustard, so you would need to add a much smaller amount. We would suggest adding a quarter of a teaspoon of either grated horseradish or wasabi paste and then tasting the dressing and adding extra to your own taste. You want a bit of a kick without it being overpowering. Please also note that some people who have a mustard allergy are also allergic to horseradish and wasabi (they come from the same Brassicaceae family), so please do check before using.