Cheesy Beef Burger & Truffle Mayo

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), the salt, egg and 1/2 the rosemary. Season with pepper. Shape the beef mixture into evenly sized patties, slightly larger than a burger bun (1 per person). Set aside.

Place the grated Parmesan cheese in even circles (about the same size as a burger bun, 1 per person) on a second lined oven tray. Bake until the cheese is golden and crisp at the edges, 6-8 minutes. Remove from the oven and set aside, they will harden as they cool.

TIP: Keep an eye on the crisps, 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, until softened, 4-5 minutes. Add the balsamic vinegar, the 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 medium high heat. Cook the beef patties until just cooked through, 4-5 minutes each side. Meanwhile, place the bake-at-home burger buns on a wire rack in the oven until heated through, 3 minutes. Thinly slice the tomato.