Preheat your oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper. Gently wipe mushrooms clean with a damp paper towel (avoid submerging in water). Snap off the stems and finely chop 1/2 cup of the stems for the filling.

Heat 1 tablespoon of olive oil in a small skillet over medium heat. Sauté the finely chopped mushroom stems and minced garlic for 3 minutes until soft and fragrant with no liquid remaining. Remove from heat and allow to cool for 5 minutes.

In a mixing bowl, combine softened cream cheese, shredded mozzarella, 1/4 cup grated parmesan, the sautéed garlic-stem mixture, chopped parsley, thyme, black pepper, and onion powder. Mix with a spatula until smooth, creamy, and thoroughly combined.

Toss the cleaned mushroom caps in 1 tablespoon of olive oil with a pinch of salt. Arrange them cavity-side up on the prepared baking sheet. Using a small spoon or cookie scoop, mound a generous tablespoon of filling into each mushroom cap.

In a small dish, toss panko breadcrumbs with melted butter and the remaining 1/4 cup grated parmesan cheese. Sprinkle a generous pinch of the buttery panko over the top of each stuffed mushroom.

Bake for 18 to 20 minutes until the mushrooms are tender and juicy, the cheese filling is bubbling hot, and the panko-parmesan tops turn crispy golden brown. Optional: Broil on high for 1 to 2 minutes for extra deep blistered crust.

Transfer to a warm serving platter, scatter extra fresh parsley, and serve warm with party picks!