1Season the beef mince with a generous pinch of salt and pepper into a medium mixing bowl. Mix well to combine, then shape into two even patties. Transfer to a plate, ready to cook.
2To make the caramelised onions, melt the butter in a large frying pan over medium heat. Add the onions, brown sugar and balsamic vinegar and cook for 2-3 minutes. Reduce the heat to low and cook for a further 7-8 minutes, or until softened and caramelised. Transfer the caramelised onions to a small bowl and set aside.
3Wipe out the frying pan, then heat a drizzle of olive oil over medium-high heat. Add the burger patties to the pan and cook for 4-5 minutes per side, or until cooked to your liking. Once browned and cooked through, add the cheese slices to the top of the burger, then cover the pan with a lid to melt. Remove from the heat.
4While the burger patties are cooking, add the burger buns to a wire rack in the oven and bake for 4-5 minutes to toast.
5Toss your cooked chips in a large bowl with the rosemary and salt.
6Assemble the burgers by spreading truffle aioli on the toasted burger bun, topping with the caramelised onions and beef patty with melted cheese. Serve with rosemary chips on the side.
