This is a rump steak sandwich built around slow-cooked balsamic caramelised onions — the kind that go properly sticky and sweet after a long, patient time in the pan. The steak is pan-fried fast and served pink, the whole thing piled onto warm ciabatta with fresh rocket. The onions are the reason to make this.
Why this recipe works
Two things carry this sandwich. First, the onions are cooked low and slow — butter, balsamic vinegar, and a little brown sugar over moderate heat for the better part of 40 minutes. That time is non-negotiable. Rush it and you get soft onions; give it the full time and you get a deeply savoury, jammy glaze that makes the whole sandwich. Second, the steak goes into a very hot pan with a high-smoke-point oil — not extra virgin olive oil, which burns at searing temperatures and turns bitter. A neutral oil like sunflower or regular olive oil keeps the crust clean and the flavour honest. The pan juices go straight onto the bread. That’s where the name comes from, and it’s worth every drop.
About the ingredients
- Rump steak: A good choice here — it has more flavour than sirloin at a lower price, and it handles a hot pan well. Buy it at least 2cm thick so it stays pink inside while the outside browns properly.
- Ciabatta: The open crumb soaks up the pan juices without going immediately soggy. A sturdy sourdough roll works too. Avoid anything too soft or the whole sandwich collapses.
- Balsamic vinegar: Use 2 tablespoons — a standard supermarket balsamic is fine. The long cook time concentrates it, so there’s no need to spend money on aged varieties.
- Rocket: Adds a peppery bite that cuts through the richness of the steak and onions. Baby spinach is a milder swap if you’re feeding people who find rocket too sharp.
- Brown sugar: Helps the onions caramelise evenly. Light or dark both work — dark gives a slightly deeper, more molasses-forward flavour.
Storage and reheating
The caramelised onions are the component worth making ahead — they keep in an airtight container in the fridge for up to 5 days, and the flavour actually improves after a day or two. They also freeze well for up to 3 months; portion them into small freezer bags and defrost overnight in the fridge. Reheat gently in a small pan over low heat with a splash of water to loosen them. Cooked steak is best eaten the same day, but if you have leftovers, slice it cold and store it separately from the bread — it keeps in the fridge for up to 2 days and makes a decent cold sandwich. Never store assembled sandwiches; the bread goes soft within an hour.
Troubleshooting
- Onions are browning too fast and catching on the bottom: The heat is too high. Drop it to low, add a small splash of water, and scrape up any stuck bits — those are flavour. The onions need time, not heat.
- Steak is grey all the way through instead of pink: The pan wasn’t hot enough before the steak went in, or the steak was cold from the fridge. Always bring steak to room temperature for 20–30 minutes before cooking, and wait until the oil is visibly shimmering before it goes in.
- Ciabatta is too hard after warming: Wrap it loosely in foil before putting it in the oven — this traps a little steam and keeps the crust crisp without drying the crumb out. Skip the garnish of extra balsamic drizzled on top at the end — not worth the extra dish.
- Sandwich is too wet and falling apart: Let the steak rest for at least 5 minutes before slicing, and slice it against the grain. This controls how much juice runs out at once. Toast the cut side of the ciabatta briefly in the dry pan after the steak comes out — 30 seconds is enough to give it a little resistance.
- Onions taste sharp or vinegary rather than sweet: They haven’t cooked long enough. The acidity of the balsamic needs time to mellow and reduce. Keep going on a low heat — another 10 minutes usually fixes it.
Dripping Steak Sandwich with Caramelised Onions
Ingredients
Caramelised Onions Ingredients
- 5 medium onions both red and white
- 2 tablespoons balsamic vinegar
- 2 tablespoons butter plus a little extra for later
- 2 tablespoons olive oil extra virgin
- 1 teaspoon sea salt adjust to taste
- 1 teaspoon freshly ground black pepper
- 1 tablespoon brown sugar
- 4 sprigs fresh thyme optional
Steak Sandwich Ingredients
- 14 oz rump steak approximately 100g per person
- 2 tablespoons olive oil light/refined, or use a neutral high-heat oil such as vegetable or canola
- 1 teaspoon sea salt
- 1 teaspoon black pepper
- 2 large handfuls fresh wild rocket (arugula) or use watercress as an alternative
- 1 loaf ciabatta bread or 4 ciabatta rolls
Instructions
Caramelised Onions Instructions
- Peel and slice the onions into about 2-centimetre rounds.
- Add 2 tablespoons of olive oil and 2 tablespoons (30g) of butter to the bottom of a large deep pan over medium heat. Once the butter has melted, arrange the onion slices to fit snugly.
- Pour over 2 tablespoons (30ml) of balsamic vinegar and tuck the thyme sprigs between the onions.
- Fry on high heat for 4 minutes, then turn the heat down and cook slowly without turning the onions.
- After about 20 minutes, turn the slices around, add in the sugar, a little more butter and salt and pepper.
- Turn up the heat again for 4 minutes, then right down for another 15 minutes until the onions are syrupy and golden.
Steak Sandwich Instructions
- Rub the steak with 1 tablespoon of olive oil and season. Over hot coals or a screaming hot pan, drop your steak and do not touch it for 2 minutes.
- After this initial hard sear to build a flavourful crust, turn the steak over and sear it for 1 minute, depending on thickness, then remove immediately and allow to rest, loosely covered with foil, in a warm spot for at least 5 minutes. For rare, aim for 3–4 minutes total. For medium-rare, cook for 4–5 minutes total. For medium, cook 5–6 minutes total. Cooking times will vary depending on steak thickness — use an instant-read thermometer for accuracy: 50°C / 120°F for rare, 55°C / 130°F for medium-rare, 60°C / 140°F for medium.
- While the steak is resting, warm the ciabatta slightly in a hot oven at 200°C / 400°F (180°C fan-forced) for 3–4 minutes until just warmed through and lightly crusty on the outside. Halve and place in those meaty pan juices (if you have any), then pile the caramelised onions on the base. Thinly slice the steak and arrange it over the onions, finishing your sandwich with a generous handful of fresh rocket (arugula).
- Press the top half of the ciabatta over the fillings, press down gently so the bread soaks up the juices, and dig in immediately while everything is still warm.
Nutrition
Frequently asked questions
Can I make the caramelised onions the day before?
Yes — and it’s actually the best way to approach this recipe if you’re cooking for a group. Store them in a sealed container in the fridge for up to 5 days and reheat gently in a pan with a splash of water before serving.
What cut of steak can I use instead of rump?
Sirloin works well and is slightly more tender, though it costs more. Flat iron steak is another good option — good flavour, handles high heat well, and is usually cheaper than sirloin. Avoid braising cuts like chuck, which need long, slow cooking to become tender.
How do I know when the steak is cooked to medium-rare without a thermometer?
Press the centre of the steak with your finger — medium-rare feels like the fleshy base of your thumb when your hand is relaxed. For a 2cm rump steak in a very hot pan, that’s roughly 2–3 minutes per side, then 5 minutes resting off the heat.
Can I cook the steak in the same pan as the onions?
No — cook them separately. The onions need a moderate heat for a long time; the steak needs the highest heat you can get for a very short time. Combining them means one or the other will be wrong. Use a second pan for the steak, or finish the onions first and set them aside while you get the pan screaming hot for the steak.
If you liked this one
- Hearty Shepherd’s Pie
- Caramelized Brussels Sprouts with Balsamic Glaze
- Rustic Sourdough Focaccia with Rosemary and Sea Salt
- Sweet and Tangy Grape Chicken Salad
