Preheat oven to 400°F (200°C).
Toss the sliced shiitake mushrooms with olive oil, salt, and black pepper, ensuring an even coating.
Spread the mushrooms on a baking sheet in a single layer and roast for 15-20 minutes, or until crispy.
In a large bowl, combine mixed salad greens, cherry tomatoes, and avocado slices.
Add the crispy shiitake mushrooms on top of the salad.
Drizzle with balsamic vinaigrette and toss gently to combine.
Serve immediately and enjoy!