Preheat oven to 240 °C or 220 °C °C fan bake. Line an oven tray with baking paper.
Make fries
Wash and cut the unpeeled potato into 1cm fries. Place on the prepared oven tray and drizzle with 1 tbsp olive oil, season with salt and pepper, and toss to coat. Bake for 20-25 minutes or until golden and cooked through.
Make caramelised onion
Peel and slice 4 red onion. Heat 1 tbsp olive oil in a pot over medium heat. Add the onions and cook for about 10 minutes, stirring occasionally, until golden brown and soft. Add 3 tbsp balsamic vinegar and 2 tbsps maple syrup, and cook a further 2-3 minutes, until very soft. Season with salt to taste. Set aside
Cook beef
Heat a frypan on medium-high heat. Drizzle 500 g beef sirloin steak with 1 tbsp olive oil and season with salt and pepper. Add to the pan and cook for 2-3 minutes on each side or until cooked to your liking. Set aside to rest for 5 minutes before very thinly slicing.
Toast buns
Slice 4 ciabatta buns in half and place on an oven tray above the fries for 5-10 minutes or until golden brown. Slice 50 g cheddar cheese.
To serve
Top the bottom buns with the caramelised onion, sliced cheese, sliced beef and mixed green salad. Place the top halves of the rolls on top, and serve fries and leftover salad on the side.