Shake Shack finally adding avocado -- and 2 limited-time sandwiches that feature it

The culinary team said avocado will now be a permanent add-on to any sandwich.

The Shake Shack team is at it again, this time finally adding to its offerings one of the most highly requested items: avocado.

The fast-casual burger joint will be offering the new avocado bacon burger and avocado bacon chicken sandwich at all U.S. locations through June 30.

Both sandwiches are topped with freshly sliced avocado and feature applewood-smoked bacon from Niman Ranch, a network of over 740 small family farmers and ranchers who raise sustainable and Certified Humane livestock.

The burger also gets a slathering of the signature Shack Sauce (pricing starts at $7.89), and the chicken sandwich comes with lettuce, pickles and buttermilk herb mayo (starting at $8.79).

Shake Shack's culinary team told "Good Morning America" that with avocado being "one of the most-requested items to date" that it will stay on the menu permanently as an add-on for any sandwich at $1.25.