- Mix mayonnaise and garlic together in a small bowl.
- Melt butter in a pan over medium low heat. Add onions and stir to coat in butter. Place lid on and leave for 20 minutes, stirring every now and then, until onion is golden (increase heat slightly if the colour is not changing).
- Add sugar, vinegar, salt and pepper. Cook for a further 10 minutes until jammy. Remove from heat and keep warm.
- Take beef out of fridge 20 minutes before cooking. Season generously with salt and pepper.
- Heat oil in a pan over high heat (or heat BBQ). Cook steak to your liking (hint: it’s best when cooked to medium rare).
- Transfer beef to a plate, cover loosely with foil and rest for 5 – 10 minutes. Then slice thinly against the grain.
Assemble sandwiches however you like and enjoy!
Note: For a vegetarian option, try grilled eggplant instead of steak.