Prepare the Chicken:
1. Preheat the oven to 400°F (200°C).
2. Place the chicken tenderloin on a baking sheet lined with parchment paper.
3. Drizzle with 1/2 tablespoon olive oil and season with salt and pepper.
4. Bake for 15-20 minutes, or until the chicken is cooked through and juices run clear.

Cook the Mushrooms:
1. In a medium skillet, heat 1/2 tablespoon olive oil over medium heat.
2. Add the sliced mushrooms and cook for 5-7 minutes, or until they are browned and tender.
3. Season with salt and pepper to taste.

Sauté the Spinach:
1. In the same skillet, add the minced garlic and sauté for 1 minute until fragrant.
2. Add the fresh spinach and cook until wilted, about 2-3 minutes.
3. Season with a pinch of salt and pepper.

Fry the Egg:
1. In a small non-stick skillet, fry the egg to your desired doneness.
2. Season with salt and pepper.

Assemble the Bowl:
1. In a large bowl, arrange the baked chicken tenderloin, sautéed spinach, and cooked mushrooms.
2. Add the diced avocado and the fried egg on top.

Serve:
Serve immediately and enjoy this delightful and nourishing breakfast bowl!