Cheesy Beef Burger & Truffle Mayo with Caramelised Onion & Potato Chips

While the fries are baking, pick and finely chop the rosemary leaves. Thinly slice the brown onion. In a large bowl, combine the beef mince, fine breadcrumbs (see ingredients), salt, egg, 1/2 the rosemary and a good pinch of pepper. Shape the beef mixture into evenly sized patties (1 patty per person), slightly larger than your burger buns. Set aside.

TIP: Make a shallow indentation in the centre of each patty to help prevent it puffing up as it cooks.

Place the grated Parmesan cheese in even circles (about the same size as your buns, 1 per person) on a second oven tray lined with baking paper. Bake until the cheese is golden and crisp at the edges, 6-8 minutes. Remove from the oven and set asidethe Parmesan crisps will become crisp as they cool.

TIP: Keep an eye on them, they can burn quickly!

While the Parmesan crisps are baking, heat a drizzle of olive oil in a large frying pan over a medium-high heat. Cook the onion and remaining rosemary, stirring often, until softened, 4-5 minutes. Add the balsamic vinegar, water and brown sugar and mix well. Cook until dark and sticky, 3-5 minutes. Transfer to a small bowl.

Wipe out the frying pan and return to a mediumhigh heat. Add the beef patties and cook until just cooked through, 4-5 minutes each side. While the patties are cooking, place the bake-at-home burger buns on a wire rack in the oven until heated through, 3 minutes. Thinly slice the tomato.