What's the Secret of McDonald's Egg McMuffin?

McDonald's Egg McMuffin is one of the fast-food chain's hottest-selling items, especially since they started serving breakfast any time of day. It's also the only sandwich that automatically comes with a freshly cooked egg.

Most eggs you order at the chain are "folded," that is, eggs that are cooked and folded into the square shape used on most McDonald's breakfast items. Folded eggs are pre-made and frozen, then shipped to each location. While these eggs do come from real eggs, they also contain a few extras: nonfat milk, modified food starch, salt, and citric acid to be exact.

McDonald's Egg McMuffin
Instagram: McDonald's

If you're looking for the freshest egg with nothing but egg in it, go for a "round egg." The round egg is cooked on site, but it's not named so for the fact that it comes directly from a shell egg. The name comes from the cooking technique, which uses a round ring on the grill to get the perfect shape for the McDonald's Egg McMuffin.

The process to cook the eggs for the chain's signature breakfast sandwich is carefully thought out and executed and, according to McDonald's restaurant employees, takes some training and practice to get exactly right. A set of eight rings is placed on the grill and real butter is misted over the grill and rings. One Grade A egg is cracked into each of the rings and the yolks are broken to make sure all eight eggs cook at the same pace.

The next step is to use a specially-created tool that sprays a specific amount of water onto the eggs so that they both steam and poach, and then the grill cover is lowered in order to cook the eggs equally on both sides, which takes about two minutes.

When the eggs are finished cooking, they go into a bin that keeps them warm while the rest of the Egg McMuffin is assembled, which involves searing the Canadian bacon on the grill, toasting the English muffins with real butter, and then adding the American cheese (which is specially made for McDonald's Egg McMuffin so that it melts when added to the toasted English muffin and egg to form almost a sauce for the sandwich.

Here's the cool secret about this little-known fact--you can add a round egg to any breakfast sandwich. It automatically comes with the Egg McMuffin and Sausage McMuffin with Egg, but you can ask for it with any of the biscuit, bagel, or McGriddles sandwiches. You can also try adding it to any sandwich or burger on the McDonald's menu, which sounds like an awesome hack to know.

What #AllDayBreakfast means to me ?? #DoubleCheese #RoundEgg #McDonalds

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And if you're looking for a healthier option as part of a fast food breakfast, the nutrition information for McDonald's Egg McMuffin shows that it's actually a pretty good option. Yes, it is heavy on the sodium and cholesterol, but according to the chain's nutrition calculator, at 300 calories it's a reasonable option, plus it's packed with protein (18 grams) and vitamin A and calcium (you get 15 percent daily value for each of those).

Watch: The 10 Best Items on the McDonald's Secret Menu.

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