Open Beef Sandwich with Caramelised Onion and Béarnaise Sauce

Steps

1. oven to 180°C (if not using BBQ). Line an oven tray with baking paper. Preheat BBQ grill to high (if using).
2. Heat a drizzle of olive oil in a small pot on medium heat. Cook onion, stirring occasionally, for 5 minutes until soft and starting to colour. Add balsamic vinegar and sugar, reduce heat to low and simmer gently for 10 minutes until thickened and glossy, stirring often to avoid burning.
3. Pat beef dry with paper towels, season with salt and pepper and rub with a drizzle of oil. Heat a medium fry-pan on medium to high heat. Cook beef for about 2 minutes each side for medium-rare (depending on thickness), or until cooked to your liking. Alternatively cook on BBQ grill. Wrap in foil to rest for 5 minutes before slicing thinly against the grain.
4. While beef is cooking, place sourdough directly on oven rack and bake for about 5 minutes until warmed through. Remove from oven, allow to cool slightly, and then cut into 1.5cm-thick slices. Alternatively, cut bread into 1.5cm thick slices, drizzle with oil and toast on BBQ grill for about 1 minute each side until toasted.
5. While steak is resting, prepare vegetables; roughly tear lettuce leaves; slice tomato and cucumber. Place all on a serving platter.
6. Take a piece of sourdough and top with sliced beef, caramelised onions and béarnaise sauce. Divide salad between plates and drizzle with more béarnaise. Alternatively place salad ingredients directly into sandwich. Top with more sourdough if desired.