Heat the oil in a frying pan and fry the onion for 5 -7 minutes, add the Walnuts and fry for a further 1 minute. Transfer to a bowl and mix in the gherkin, mustard, 1 tbsp water and parsley, season.
Cook the frankfurters on a BBQ or griddle pan for 5-8 minutes, turning until evenly cooked. Serve in the buns topped with the Walnut mustard relish.
Notes
Cook’s tip: Add tomato sauce to the buns before adding the frankfurters if liked. The relish can be made ahead and kept in the fridge until needed.2.2g salt per serving