I tried the recipe again, this time using shiitake mushrooms in the place of the green beans. Certainly nowhere near as colorful as a photo.
Unfortunately, it wasn't as flavorful either. The shiitakes added a woody flavor to an already woody dish. It really made me appreciate what green beans added to the dish. I think if I added button mushrooms rather than shiitakes it could add a brighter flavor. It will be something to try.