McDonald’s made waves when it extended its breakfast hours in 2015 to include all-day McMuffins instead of cutting the morning foods off at 10:30 a.m. If the later hours mean you’ve been ordering from the fast-food chain’s breakfast menu more often, you might want to know a secret about its eggs.

After questions arose about whether or not McDonald's used fresh eggs in its sandwiches, the fast-food giant was quick to release information about their breakfast foods. A video released by the company and confirmed by CNBC showed a tour of their supplier's eggs and confirmed that whole eggs were used in all breakfast items. But that wasn't the whole story.

While many eggs that meet requirements are sent directly to McDonald's locations, those that aren't are broken and mixed with additional ingredients including modified food starch, salt, and citric acid, and then made into the "folded egg" that is used on most McDonald's breakfast sandwiches. The folded eggs used in biscuit, bagel, and McGriddle sandwiches are cooked in another location, then frozen and shipped to the McDonald’s restaurants, according to the company.

The scrambled egg sausage mix in a McDonald's breakfast burrito is also precooked by food suppliers, then mixed in with other ingredients such as meat, vegetables, spices, sugar, and additives—including dextrose and xanthan gum—before being frozen. Restaurants microwave the egg mix to reheat it. F

Scrambled eggs, like the ones in the Big Breakfast, come closer to fresh, though they aren't cracked from the shell on location. They come in a liquid with minimal ingredients (just eggs and the preservative citric acid), which is cooked with butter on the grill.

However, there is one recipe you can get from McDonald's to ensure your egg is freshly cracked on site. To get the freshest egg possible, you’ll want to order a McMuffin. Unlike the other breakfast sandwiches, McMuffins are made with “round eggs”: a whole egg cracked into a metal egg ring that keeps the egg in the right shape. If you order yours with egg whites, your protein won’t come from a fresh-cracked egg, but the egg white liquid doesn’t contain any extra ingredients. A McDonald's owner and operator from Canada even demonstrated how the process worked during an egg cracking competition he held at his branch and posted online. You won't want to miss the reason McDonald's almost didn't add the McMuffin to its menu.

Want a freshly cracked egg but prefer a McGriddle or biscuit base? There's no need to worry. “If you want real eggs on your breakfast sandwiches instead of the liquid stuff, you can put a round egg onto any breakfast sandwich,” former McDonald’s employee Chuck Chan reveals on Quora. “Just ask for a ‘round egg’ on it.”

Related video: The 'World’s Smallest McDonald's' Is Now Open — to Bees [via Food&Wine;]