This was my first mushroom burger ever.
According to the menu, the burger is made of a fried portobello that is filled with muenster and cheddar cheese, and topped with lettuce, tomato, and ShackSauce.
The mushroom itself had a good crunch, but I couldn't describe it beyond "fried."
Fortunately, the texture was not slimy, and the flavor was elevated by the smokiness of the two kinds of cheese.
If I were a vegetarian, I think I would be happy ordering this for lunch.