Parmesan cheese may seem a little unusual in this recipe, but it really gives the burgers a great flavour – give it a bash.
Grind up the red chilli in a pestle and mortar, and mix it in a bowl with the onion, tarragon, egg, breadcrumbs, mustard, Parmesan, nutmeg and beef. Shape into four patties and refrigerate for half an hour or so to give them a chance to firm up slightly.
When you're ready to cook the burgers, get a frying or griddle pan nice and hot. Brush the pan with a little oil, season the burgers generously with salt and pepper, and cook them for 10 minutes, turning them carefully every minute or so, until they're nice and pink and juicy, or longer if you like them well done. Make sure they don't break up as you turn them.
Meanwhile, roughly chop the lettuce, tomato and cucumber, mix together and set aside. Once the burgers are cooked, split the rolls into two and toast them quickly on the griddle or in a toaster. Sandwich the cooked 'Elvis' burger between the toasted rolls and serve them on individual plates with the gherkins and some of the chopped salad (add a little extra virgin olive oil or dressing if you like) on the side.