Mcdonalds is selling a new big mac with four patties

I think there may be some confusion here!

McDonald's has not announced a new Big Mac with four patties. The classic Big Mac has two all-beef patties, special sauce, lettuce, cheese, pickles, and onions on a sesame seed bun. While McDonald's has introduced various limited-time offers and regional variations of the Big Mac over the years, a four-patty version is not a known or announced variation.

It's possible that you may have seen a concept design or a fan-made creation of a four-patty Big Mac online, but it's not an official product from McDonald's.

If you're interested in trying new and innovative menu items, you can always check out McDonald's website or social media channels for updates on their latest offerings!