Preheat broiler, setting temperature to high. Set oven rack in the middle of the oven. Line a baking sheet with foil
Spray the mushroom caps with olive oil cooking spray on both sides
Sprinkle with ¼ teaspoon kosher salt, ⅛ teaspoon pepper and ¼ teaspoon garlic powder
Broil 5 minutes on each side, or until just tender
Remove mushrooms from oven
Switch oven from broil to bake, setting temperature to 400 degrees
Break an egg into each mushroom
Sprinkle with cheese
Bake 15 minutes, until egg whites are cooked
Sprinkle the eggs with the remaining ¼ teaspoon salt and ⅛ teaspoon pepper
Garnish with parsley, and serve