Flat Iron has brought its latest annual burger to Brighton, combining two beef patties with onions smashed directly onto the meat, cheese, pickles and a ketchup béarnaise.
Brighton diners can now try Flat Iron’s latest once-a-year burger change at the steak restaurant in The Lanes.
The Smashed Onion Double Cheeseburger launched nationally on Tuesday 7 July and remains listed on Flat Iron’s current menu at £14.
For Brighton, there is a little more significance to the launch. Flat Iron opened its Ship Street restaurant in October 2025, meaning this is the first of the group’s annual burger launches to reach the city since the Brighton branch opened.
| Dish | Smashed Onion Double Cheeseburger |
|---|---|
| Price | £14 |
| Where | Flat Iron, 34 Ship Street, Brighton, BN1 1AD |
| What’s in it? | Two beef patties, smashed onions, cheese, mustard, pickles, ketchup béarnaise and crispy batter scraps |
| Calories | 796 kcal, according to Flat Iron’s current menu |
| Current Brighton hours | Sunday to Thursday 12pm–10pm; Friday and Saturday 12pm–11pm |
What’s in Flat Iron’s smashed onion burger?
The burger starts with two patties made using beef from Flat Iron’s own herd in North Yorkshire.
Rather than adding fried onions afterwards, thin slices of sweet white onion are smashed directly into and around the beef as it cooks.
The technique means different pieces of onion cook in different ways: some caramelise against the hot cooking surface, others soften into the meat and some retain more texture.
The patties are then topped with American mustard and cheese, sliced pickles, ketchup béarnaise and crispy batter scraps.
The final two ingredients provide a link with Flat Iron’s previous Béarnaise Burger, which appeared as an earlier annual burger special.
What does £14 get you?
Two Flat Iron Herd beef patties with smashed sweet onion, cheese, mustard, pickles, ketchup béarnaise and crispy batter scraps. Sides are ordered separately.
Why are the onions smashed into the beef?
The method takes its inspiration from the American fried onion burger, where thinly sliced onions are pressed directly into the beef while it cooks rather than simply being placed on top afterwards.
Flat Iron’s Head of Beef, Fred Smith, said the team spends months refining the burger it introduces each year.
He said the 2026 version was intended to concentrate on the combination of beef, onion, mustard and cheese, with the cooking technique providing additional depth of flavour and the ketchup béarnaise adding richness.
Flat Iron’s Brighton restaurant
Flat Iron opened in Brighton in October 2025, taking a two-floor site at 34 Ship Street in the heart of The Lanes.
The restaurant is close to The Ivy and within a short walk of Brighton seafront, The Lanes and the Royal Pavilion.
Flat Iron began as a London pop-up in 2012 before developing into a restaurant group built around relatively simple steak menus and British and Irish beef.
The Brighton restaurant follows the same model, with the signature Flat Iron steak joined by changing beef specials and sides including beef-dripping chips, crispy bone-marrow garlic mash, creamed spinach and truffled macaroni cheese.
The group’s current menu lists the Smashed Onion Double Cheeseburger among its beef specials alongside a 35-day-aged ribeye and Wagyu steak of the day.
How much is the Flat Iron burger?
The Smashed Onion Double Cheeseburger is currently listed at £14.
That price is for the burger itself. Flat Iron’s sides are ordered separately, with its current menu listing beef-dripping chips and creamed spinach at £4.50, while crispy bone-marrow garlic mash and truffled macaroni cheese are £5.
The burger itself is listed at 796 calories, before any sides, sauces or drinks are added.
Allergy information
Flat Iron’s current allergen information lists the Smashed Onion Double Cheeseburger as containing celery, milk, eggs, cereals containing gluten, mustard, soya and sulphur dioxide. It may also contain traces of nuts and sesame.
Anyone with a food allergy or intolerance should check the restaurant’s current allergen information and speak to staff before ordering rather than relying solely on a published menu description.
Frequently asked questions
What is Flat Iron’s new burger?
The 2026 annual burger is the Smashed Onion Double Cheeseburger, made with two beef patties, onions smashed into the beef while cooking, cheese, mustard, pickles, ketchup béarnaise and crispy batter scraps.
How much is the Smashed Onion Double Cheeseburger?
Flat Iron’s current menu lists it at £14. Sides and drinks are additional.
Can you get the Flat Iron burger in Brighton?
Yes. It is available at Flat Iron Brighton on Ship Street and remains listed on the restaurant group’s current menu.
Where is Flat Iron Brighton?
Flat Iron Brighton is at 34 Ship Street, Brighton, BN1 1AD, in The Lanes.
When is Flat Iron Brighton open?
The restaurant currently lists opening hours of noon to 10pm from Sunday to Thursday and noon to 11pm on Friday and Saturday.
Does the £14 burger come with chips?
No. The burger is listed separately, with sides such as beef-dripping chips available at additional cost.
Menu prices, opening hours and availability checked in September 2026. Restaurant menus and prices can change, so check Flat Iron’s current menu before making a special journey.
You May Also Be Interested In
