Shake together all ingredients or blend with hand blender for a thicker, creamier emulsion.
Variations: For a cost-effective dressing, substitute the walnut oil for more olive oil; add your favourite herbs, eg. parsley, chives, oregano, basil, etc. ; replace smooth Dijon mustard with coarse-grain Dijon mustard for potato salads; reduce oil and add 4 tablespoons Fromage Frais or Creme Fraiche - drizzle over ostrich or beef carpaccio.