ST. PAUL, Minn.- It's been around for decades and is still the most popular item on the McDonald's menu... the Big Mac.

You may even remember their catchy jingle... "Two all beef patties, special sauce, lettuce, cheese, pickles, onions, on a sesame bun."

"The Big Mac was developed by an owner operator so it was locally created in Pittsburgh in 1967, so its 50 years old and its so popular that it expanded nationwide just a year later," said Yasmin Hyder, McDonald's Owner.

So why are we talking about this iconic sandwich?

J.Selby's, a new restaurant in St. Paul, is growing in popularity thanks in part to their own version of the Big Mac. The only difference... it's made entirely from plants and it's known as the "Dirty Secret".

"What is a dirty secret for many vegans is that they kinda want to eat a Big Mac and we reimagined it as plant based... so we use the herbivorous butchers beef patties, and cheese, and fresh toppings," said J.Selby's owner Matt Clayton.

So how does the "Dirty Secret" stack up with the Big Mac? The MacDonald’s classic is higher in fat (28g) and calories (540), but lower in protein (25g) and price ($4.43).

The Vegan version is lower both in fat (14g) and calories (530) but higher in protein (38g) and price ($15).