Preheat your oven to 400°F (200°C) to ensure crispy mushrooms.
Line your baking sheet with parchment paper for easy cleanup.
In a large bowl, combine the Panko breadcrumbs, grated Parmesan cheese, garlic powder, salt, pepper, and dried parsley. Mix well.
In a separate bowl, whisk the egg whites until frothy.
Clean the mushrooms gently with a damp paper towel. Remove stems if desired.
Dip each mushroom into the egg whites, then roll in the breadcrumb mixture. Place on the prepared baking sheet.
Bake for about 15-20 minutes until golden brown and crispy, flipping halfway through.
Remove from the oven, let cool slightly, and serve warm.
