Preheat the oven to 180°C.
Break up the patties and reshape into 4 large patties.
Heat the butter and oil in a large ovenproof pan and cook the patties for 5 minutes on each side, or until cooked through. Pour in the plum sauce, transfer to the oven and roast for 10 minutes, or until done to your liking.
Top each patty with 2 slices of cheese.
Spread the sriracha mayo onto the bottom halves of the rolls. Mix the mayonnaise and horseradish and spread onto the top halves of the rolls.
Place a patty on the bottom halves of the rolls, then add the lettuce, tomato, pesto, onion and gherkins and the top halves of the rolls.
Cook's note: The perfect burger is all about the balance between a juicy patty, the perfect texture, crunch and flavour.
This recipe graces the cover of the September 2018 issue of TASTE Magazine - on sale now!