Fast food fans were delighted to hear McDonald's was bringing out a new McMuffin just in time for Christmas.
The new Mighty McMuffin was added to the chain's breakfast menu on Wednesday November 23, joining classic items such as the traditional McMuffin, the Breakfast Roll and the Pancakes and syrup.
A McDonald's worker recently took to TikTok to show how the new Mighty McMuffin is assembled before it's presented to hungry customers.
As fans would expect, the item consists of sausage, egg, bacon, cheese and ketchup or brown sauce. However, as foodies were finally given a look behind the scenes, they could see one more thing they hadn't expected.
Before the McDonald's worker, who posted the video on the TikTok channel @mcdonalds0851, added the main items, they could be seen squirting some sort of clear liquid onto the English muffin.
They then proceeded to add the sauce on top of the liquid, before adding the rest of the items.
At the end, viewers could see the whole itemised list of things that go onto a Mighty McMuffin, which solved the mystery of what the liquid was – Roast 'n Fry.
Curious McDonald's fans took to the comment section, which has now been turned off on the video, to ask if anyone else knew what Roast 'n Fry was.
One person asked: "What is Roast 'n Fry?".
On a separate video, another McDonald's worker, who posted on the channel @ ashleyvong4, described the liquid as "butter".
McDonald's has cleared up the mystery of the liquid to The Mirror – and it turns out it's to make the treat extra tasty.
A spokeswoman for McDonald's told us: "Roast 'n' fry is a Liquid Vegetable & Dairy Fat Blend. It is only used on McMuffins, and is also used to season/oil the egg rings.
"It adds moisture to the muffin so that it’s not dry – just like you would butter your muffin or bread at home."
Fast food fans took to Twitter to share their delight about the new breakfast item.
One person said: "Mighty McMuffin is the best thing on the McDonald's menu."
A second posted: "Big thumbs up here for the new Mighty McMuffin."
You can pick up the Mighty McMuffin for £3.99 on its own, or £5.59 for a meal until 11am every day.
The burger chain also added a host of other items to the Festive Menu, including the Big Tasty, Festive Pie, Cheese Melt Dippers and Celebrations McFlurry.
Have you tried the Mighty McMuffin and what did you think? Let us know in the comments below.