Ingredients:
- 1 lb (450 g) Sirloin or Rump Steak, 1.5 inches thick
- 1 tbsp Kosher Salt & Freshly Ground Black Pepper
- 1 tbsp High Heat Cooking Oil (Rapeseed or Grapeseed)
- 1 tbsp Unsalted Butter
- 2 large Smashed Garlic Cloves, unpeeled
- 2 fresh Thyme Sprigs
- 1 large (150 g) Red Onion, thinly sliced
- 1 tsp Olive Oil
- 2 tbsp Balsamic Vinegar
- 1 tsp Brown Sugar
- Pinch of Salt
- 1 small loaf Crusty Bread (Ciabatta or Sourdough)
- 2 tbsp Good Quality Mayonnaise
- 1 tbsp Creamed Horseradish
- 1 cup (50 g) Rocket (Arugula)
Instructions:
- Prepare the Steak and Onion Jam: Pat the steak dry and season generously with salt and pepper immediately before cooking. For the jam, heat the olive oil in a small pan over medium-low heat, add the sliced red onion and salt. Cook gently until soft (8–10 minutes). Add balsamic vinegar and brown sugar; simmer until liquid reduces to a thick glaze (about 5 minutes). Set aside.
- Cook the Steak: Heat a cast iron skillet over high heat until smoking hot. Add cooking oil, then sear the steak undisturbed for 3 minutes. Flip the steak, reduce heat to medium-high. Add butter, garlic, and thyme. Baste the steak continuously with the melted butter mixture for another 2–3 minutes until the internal temperature reaches 130°F (55°C) for medium-rare. Remove the steak and tent loosely with foil to rest for 8–10 minutes.
- Toast the Bread and Assemble the Cream: Slice the bread horizontally. Lightly brush the cut sides with oil or butter and toast until golden brown. In a small bowl, combine the mayonnaise and the creamed horseradish until smooth, adjusting the spice level to your preference.
- Slice and Final Assembly: Slice the rested steak very thinly against the grain. Spread a generous layer of horseradish cream on both slices of toasted bread. Layer the bottom piece with rocket (arugula), then arrange the sliced steak evenly over the rocket. Top the steak with a generous amount of the quick red onion jam. Close the sandwich, slice in half, and serve immediately.