Cut the avocado in half lengthwise, twist to separate, and remove the pit by gently twisting it with the knife. Peel the skin and cut the avocado into large bite-sized pieces. Cut the king oyster mushrooms in half lengthwise, then into quarters.

Heat olive oil in a frying pan over medium heat. Add the king oyster mushrooms and stir-fry until softened. Add the avocado and seasonings (lemon juice, soy sauce, black pepper, and garlic) and stir until well combined.