The following is the e-mail response from Cheeburger Cheeburger when asked which of their menu items are vegan:
Thank you for your interest in our menu. None of our menu items contain L-Cysteine other than those in which it is found naturally – products such as meat, proteins and cheeses. We do offer a variety of delicious salads and several portabella mushroom plates to cater to our Vegan guests. While we don’t have a dedicated area for preparing Vegan offerings we will do our best to accommodate our guest’s needs.