Preheat the oven to 400°F (200°C) and lightly grease a large rimmed baking sheet with olive oil.

Clean the mushrooms with a damp paper towel to remove debris. Remove the stems from the mushrooms and finely chop them, setting the caps aside.

In a medium skillet, heat the olive oil over medium heat. Sauté the chopped mushroom stems and minced garlic for 5 minutes or until moisture has evaporated and stems are tender.

In a medium mixing bowl, combine the softened cream cheese, sautéed stems and garlic, Parmesan cheese, onion powder, black pepper, and salt. Stir until the mixture is uniform.

Using a small spoon or piping bag, fill each mushroom cap with a generous amount of the cream cheese mixture.

Dip the cheese-filled side of each mushroom into the Panko breadcrumbs, pressing lightly so they adhere.

Arrange the stuffed mushrooms on the prepared baking sheet and bake for 20 minutes until the mushrooms are soft and the breadcrumb topping is golden brown.

Garnish with fresh chopped parsley and allow to rest for 5 minutes before serving.