Chipotle began testing its tofu-based Sofritas filling yesterday at its restaurants in Baltimore, Philadelphia, Richmond, and Washington, D.C.

Since its initial launch of Sofritas at seven San Francisco Bay Area restaurants, Chipotle has added Sofritas to the menu all of its restaurants in California, Chicago, Colorado, Idaho, Oregon, Utah, Washington, and Vancouver, Canada. The East Coast expansion brings the total number of restaurants offering Sofritas to about 600, more than a third of the company’s outlets.

Sofritas – a shredded tofu braised with chipotle chilies, roasted poblano peppers and a blend of aromatic spices – is available in burritos, tacos, burrito bowls, and salads. Chipotle is sourcing the tofu for its Sofritas from California-based Hodo Soy, which produces organic, non-GMO tofu.

A spokesperson for Chipotle reports that Sofritas accounts for 4 to 5 percent of sales in the stores that offer it, which may be contributing to the the chain's growing bottom line.

Last week, Chipotle announced that its 2013 third quarter earnings topped $826 million and was up 18 percent as compared to the third quarter of 2012.