To toast the walnuts, place in a heavy-based frying pan over a medium heat and cook for 1-2 minutes, stirring, until just browned.
Replace the mayonnaise with natural yoghurt or soured cream, if you like.
Don’t just dip! Make a deluxe prawn cocktail. Place shredded lettuce in individual serving bowls then top with spoonfuls of the guac, cooked peeled prawns and slices of smoked salmon.