Ingredients:

  • 3 large Yellow Onions (approx. 600g), very thinly sliced
  • 1 Tbsp High Smoke Point Oil (for onions)
  • 1 Tbsp Unsalted Butter (for onions)
  • 1/2 tsp Sea Salt (plus more to taste)
  • 1 tsp Balsamic Vinegar (optional)
  • 2 (8 oz / 225g) Sirloin or Rump Steaks, 1-inch thick
  • 1 Tbsp High Smoke Point Oil (for searing)
  • 3 Tbsp Unsalted Butter, cold and cut into small cubes (for basting)
  • 3 sprigs Fresh Thyme
  • 2 cloves Garlic, smashed, unpeeled
  • 1 tsp Coarse Sea Salt (for seasoning the steaks)
  • 1/2 tsp Freshly Cracked Black Pepper

Instructions:

  1. Prepare the Steak: Remove the steaks from the fridge 20 minutes before cooking. Pat them completely dry with paper towels (crucial for a great crust). Season very liberally on all sides with salt and pepper.
  2. Start the Onions: In a separate medium pan, melt 1 Tbsp butter and 1 Tbsp oil over medium-low heat. Add the sliced onions and the 1/2 tsp salt.
  3. Sauté Slowly: Cook the onions, stirring occasionally, for 15–20 minutes. The heat should be low enough that they soften and sweat, not brown.
  4. Caramelise: Once soft and translucent, increase the heat slightly to medium-low. Cook, stirring every 3–4 minutes, until they turn a deep golden-brown and are jammy and reduced (about another 10 minutes).
  5. Finish Onions: Stir in the optional balsamic vinegar and cook for 1 minute. Taste and adjust seasoning. Transfer the onions to a warm bowl and cover loosely.
  6. Heat the Pan: Place a cast iron or heavy-bottomed pan over high heat. Add 1 Tbsp of high smoke point oil. Wait until the oil is shimmering and just starting to smoke.
  7. Sear the Steak: Carefully place the seasoned steaks into the hot pan. Sear undisturbed for 3 minutes for a medium-rare crust.
  8. Flip and Baste Prep: Flip the steaks. Immediately reduce the heat to medium. Add the cold butter, thyme sprigs, and smashed garlic to the pan.
  9. Baste: Tilt the pan slightly and, using a spoon, continuously scoop the melted, foaming herb butter over the top of the steaks for about 2–3 minutes until the desired doneness is reached (130–135°F / 54–57°C for medium-rare).
  10. Rest: Remove the steaks from the pan and place them on a resting board or warm plate. Tent loosely with foil. Pour any excess basting butter/juices over the onions and allow the steak to rest for 8–10 minutes.
  11. Slice and Serve: Slice the steak thinly against the grain (if using a large cut). Serve immediately alongside a generous helping of the warm caramelised onions.