Prepare the vegetables as described in the ingredients list, and heat up a large frypan or wok on medium-hot.
Start cooking the vegetables individually in small amounts of oil, starting with the onion. Cook for 1-2 minutes until soft, lightly browned and then set aside.
Next, cook the sliced shiitake in a little oil. The mushrooms should be nice and browned before removing to a plate - a few minutes.
Start cooking the next veggies in some oil - these should be cooked only about a minute to maintain crispiness. Set aside once done.