Ultimate Bacon Cheeseburger With Rosemary Salted Fries

Heat the oven to 220°C, or 200°C fan. Cut the potatoes into fries about 1 cm thick so they cook evenly. Rinse them under cold water, drain well and pat completely dry with a clean towel. Toss with 1 tablespoon of the cooking oil, half of the dried rosemary, 1 teaspoon of salt and several grinds of black pepper. Spread in one layer on a large baking tray. Bake for 35–45 minutes, turning after 20 minutes, until deeply golden and crisp at the edges.

Put the beef mince in a bowl. Add the remaining rosemary, 1/2 teaspoon salt and a generous pinch of black pepper. Mix gently with clean hands just until combined; overmixing makes burgers tough. Divide into 4 equal portions and shape into patties slightly wider than the bread rolls, pressing a shallow dip into the centre of each patty so they stay flat while cooking. Chill for 10 minutes while you prepare the toppings.

Thinly slice the onion. Slice the bread rolls in half. Grate or slice the mozzarella and cheddar so they melt quickly. Keep the burger components beside the hob before you begin cooking, because the final stages move quickly. During the last 5 minutes of the fries cooking time, place the bread rolls cut-side up in the oven for 2–3 minutes until lightly toasted.

Place the bacon in a large dry frying pan over medium heat. Cook for 6–8 minutes, turning regularly, until browned and crisp. Transfer to a plate lined with kitchen paper. Carefully pour away most of the bacon fat, leaving about 1 teaspoon in the pan for flavour.

Return the pan to medium-high heat. Add the remaining cooking oil if the pan looks dry. Cook the patties for 4–5 minutes on the first side without pressing them down. Turn and cook for another 3–5 minutes, depending on thickness, until browned and cooked through. In the final minute, divide the mozzarella and cheddar between the patties, add 1 tablespoon of water to the pan and cover with a lid for 30–60 seconds so the cheese melts. The centre of each burger should be piping hot with no raw pink meat remaining.

Place a cheeseburger patty on each toasted bottom bun. Add the sliced onion and crispy bacon, then close with the top bun. Taste one fry and add a little more salt or rosemary if needed. Serve the burgers immediately with the hot rosemary fries. Add ketchup, mayonnaise, lettuce or sliced tomato if you have them.