Prepare the crispy onions: Place the sliced red onions in a bowl and toss with the flour, ½ teaspoon of salt, and a good grind of black pepper until every sliver is lightly coated. Heat the vegetable oil in a deep, heavy-based saucepan to 180°C. Working in batches, carefully lower the floured onions into the hot oil. They will sizzle immediately and begin to turn a deep, nutty golden brown. You will hear the sizzle subside as they crisp up. Once they are a rich amber colour and feel brittle when stirred, after about 3–4 minutes, lift them out with a slotted spoon onto a plate lined with kitchen paper. They should shatter slightly when touched. Season immediately with a pinch of salt.

Season and rest the steak: While the onions cool, pat the steaks dry with kitchen paper. This is crucial for a good sear. Rub each steak with the 1 tablespoon of olive oil, then season generously on all sides with the remaining flaky salt and black pepper. Leave them to come up to room temperature for about 10 minutes. I used to struggle with this dish until I discovered this technique – a room-temperature steak cooks far more evenly than a cold one straight from the fridge.

Sear the steak to perfection: Place a heavy frying pan (cast iron is ideal) over a high heat and let it get screaming hot – you should see a faint wisp of smoke. Lay the steaks in the pan, and you should hear a powerful, satisfying sear. Do not move them for 3 minutes. Flip the steaks; the cooked side should be a deep, caramelised brown with a crisp crust. Cook for another 3 minutes for medium-rare. For medium, add a further minute per side. The smell of seared beef will fill your kitchen.

Rest the steak: Transfer the steaks to a cutting board and let them rest for a full 5–7 minutes. This is non-negotiable. As they rest, the juices will redistribute throughout the meat. If you cut into them immediately, those precious juices will run out onto the board, leaving your steak dry. The surface will feel firm but give slightly when pressed.

Make the dressing: While the steak rests, make the dressing. In a small bowl or jar, whisk together the red wine vinegar, Dijon mustard, and a pinch of salt and pepper. Slowly drizzle in the 2 tablespoons of extra virgin olive oil, whisking constantly, until the dressing is emulsified and slightly thickened. It should smell sharp and clean.

Assemble the salad: Place the mixed salad leaves in a large bowl. Drizzle over just enough of the dressing to lightly coat the leaves – you want them glistening, not drowning – and toss gently. Divide the dressed leaves between two large plates or bowls. Crumble or slice the blue cheese and scatter it over the greens.

Slice and serve: Slice the rested steaks against the grain into 1cm thick strips. The inside should be a perfect rosy pink for medium-rare, and the outside a deep, dark brown. Fan the steak slices over the dressed salad. Pile a generous handful of the crispy onions on top of each salad. Serve immediately, while the steak is still warm and the onions are at their crispiest.