n a large bowl, mix the first 4 ingredients (beef through oregano). Form beef mixture into patties.
In a large skillet over medium heat, add the burgers and cook or 5 minutes on each side, until cooked to desired level of doneness. Set burgers aside.
In the same skillet over medium heat, heat olive oil. To the oil, add the coconut aminos and the mushrooms. Cook 5 minutes, on each side, until tender.
In a large bowl, toss the remaining ingredients together and then season with salt and pepper.
On individual plates, layer the mushroom caps then the burgers. Top each burger with the arugula salad and serve.