The base of flavour to this risotto comes from plenty of porcini stock and tons of browned mushrooms. When browned well, mushrooms add so much meatiness that even the most devout of carnivores would love this vegetarian dish. I finished the dish with a nice chunk of truffle butter I received as a gift. It definitely adds even more mushroomy depth, aroma and luxury but is by no means necessary.
I used button and oyster mushrooms here just because of how easy they are to get your hands on. Adding or replacing with different varieties of edible mushrooms are strongly encouraged.