1 leek per person, cut into small pieces
1 heaped tsp. Dijon mustard (or any other kind; I do prefer the kind with seeds in it, but you could even use mustard powder instead, although arguably not so much!)
C 2 tbs wine vinegar
C 4 tbs olive oil
Steam the leeks until they are cooked. Meanwhile, put the mustard and vinegar into a blender and add the oil in a steady stream while it is running. The mustard with emulsify the mixture, which is what you want. Season as liked - I didn't think it needed any more, but you might.
Pour a judicious quantity of the dressing on to the hot leeks and stir well. You want to coat them, not give them a bath, so you may have some dressing left over, depending on how many leeks you have. Allow to cool, and refrigerate before eating. They are meant to be eaten cold.
