Drizzle a little avocado oil into a heavy cast iron pan or wok. Just a thin coating is needed so the vegetables do not stick. Toss the mushrooms into the pan. Make sure they sit there in an even layer. Allow them to cook on one side for 3-4 minutes over medium high heat. Toss them around until evenly browned. Do not add salt. When they are browned, remove them from the pan, and set aside.
You can add chicken, beef, shrimp or tofu for added protein. Tamari is gluten free soy sauce and does have a stronger flavor than regular soy. If you don't need this to be gluten free, you can use regular soy sauce.