This is not your average steak sandwich.

A beautifully seared Warrendale Wagyu Flat Iron Steak is thinly sliced and piled into a toasted sourdough bloomer with peppery rocket, melted Gruyère and sweet, sticky caramelised red onions. It's rich, buttery, cheesy and seriously satisfying. The kind of sandwich that requires both hands and absolutely no regrets.

The beauty of this recipe is that it doesn't need much. Flat Iron steak brings plenty of bold beef flavour, while the natural marbling of Warrendale Wagyu gives it an extra layer of richness and tenderness. Add a few simple ingredients and a hot grill, and you've got a proper steakhouse-style sandwich made at home.

It's also incredibly easy to scale up. Slice the finished sandwich into bite-sized pieces and serve it as a party sub, or keep the whole thing for yourself. We won't judge.

Ingredients:

• 2 large red onions
• 2 tsp red wine vinegar
• Vegetable oil
• Salt & pepper
• 1 large white sourdough bloomer
• 1 8oz Warrendale Wagyu Flat Iron Steak
• 80g Gruyère, finely grated
• Rocket
• 20g salted butter, optional

Method

1. Preheat the grill setting on your oven.

Finely slice the red onions and add them to a frying pan over a medium heat with a little vegetable oil. Slowly sweat the onions down, stirring regularly, until they begin to soften.

Add the red wine vinegar and continue cooking until the onions are soft, sticky and caramelised. Season with salt and pepper to taste, then set aside.

Don't rush the onions here. Giving them time to slowly caramelise brings out their natural sweetness, which works beautifully against the rich Wagyu and salty Gruyère.

2. Remove the Flat Iron Steak from the fridge at least 1 hour before cooking and allow it to come towards room temperature.

Heat a frying pan until it is searing hot. Lightly coat both sides of the steak with vegetable oil and season generously with salt.

Place the steak into the centre of the pan and cook to medium-rare.

For the best result, use a meat thermometer and aim for an internal temperature of approximately 52–54°C before resting. Cooking time will depend on the thickness of your steak, but around 3–4 minutes per side is a good starting point for an 8oz Flat Iron.

3. While the steak is cooking, slice the sourdough bloomer in half lengthways and place both halves, cut-side up, on a baking sheet.

Place under the grill for 4–6 minutes, or until the bread is crisp and golden around the edges.

Keep an eye on it — grills can work quickly.

4. Remove the steak from the pan and allow it to rest for at least 5 minutes.

Resting gives the juices time to redistribute through the meat, helping to keep the steak juicy when you slice it.

5. Once the bread is toasted, you can spread a little salted butter over the bottom half if you like.

However, this is completely optional. With the natural richness and buttery marbling of the Wagyu Flat Iron, you may find you don't need it at all.

6. Thinly slice the rested steak against the grain. This is particularly important with Flat Iron steak and will give you a more tender bite.

Layer the rocket over the bottom half of the sourdough, followed by the sliced Wagyu steak.

Generously cover the steak with the finely grated Gruyère, then place the sandwich back under the grill for 3–4 minutes, or until the cheese has melted and is bubbling.

7. Remove from the grill and add plenty of freshly cracked black pepper.

Spoon over the caramelised red onions and finish with the top half of the sourdough.

Slice into portions and serve immediately.

You can serve this as a party sub and cut it into bite-sized pieces for everyone to share, or simply demolish the whole thing yourself. We don't judge.

This is what great steak is all about: quality Wagyu, a few simple ingredients and absolutely no need to overcomplicate it.

Why choose Wagyu Flat Iron Steak?

Flat Iron steak comes from the shoulder, or chuck section, of the cow. It's cut from the top blade muscle and has become increasingly popular for its combination of tenderness, rich beef flavour and excellent value compared with some of the more traditional premium steak cuts.

Although the shoulder does plenty of work, the flat iron is taken from a particularly tender part of the muscle. Once the tough connective tissue running through the centre is removed, you're left with a beautifully even steak that's ideal for cooking quickly over high heat.

Flat Iron is naturally full of beefy flavour, making it a great choice for a recipe like this where the steak needs to stand up to bold ingredients such as caramelised onions and mature Gruyère.

Wagyu takes that flavour and texture a step further. Warrendale Wagyu Flat Iron contains fine intramuscular marbling: the small threads of fat running through the meat. As the steak cooks, this fat begins to render, giving the meat a rich, buttery quality while helping to keep it juicy.

It's exactly what you want in a steak sandwich. You get the deep, satisfying beef flavour of the flat iron, combined with the luxurious texture and richness you'd expect from Wagyu.

For this recipe, we recommend cooking the steak to medium-rare. A good sear on the outside and a juicy centre gives you the best texture when the steak is sliced thinly for the sandwich.

And because the steak is already so rich and buttery, you don't really need much else. The sweet caramelised onions, sharp Gruyère and fresh rocket provide enough contrast to let the Wagyu do what it does best.