Preheat your oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper. Wipe mushrooms clean with a damp paper towel (never soak in water). Gently pop out the stems and finely chop 1/2 cup of stems for the filling. Toss mushroom caps lightly in 2 tbsp olive oil and a pinch of salt; arrange hollow-side up on the baking sheet.

Heat 1 tablespoon of butter in a small skillet over medium heat. Add the finely chopped mushroom stems and minced garlic. Sauté for 2 to 3 minutes until tender and moisture has evaporated. Remove from heat and allow to cool for 3 minutes.

In a medium bowl, beat softened cream cheese, sautéed garlic-stem mixture, 1/2 cup grated parmesan, chopped parsley, thyme, onion powder, and black pepper until creamy and thoroughly blended. In a separate small bowl, toss panko breadcrumbs with 2 tbsp melted butter and 2 tbsp grated parmesan.

Using a small spoon or cookie scoop, mound a generous tablespoon of cream cheese filling into each mushroom cap. Top each stuffed mushroom generously with the buttered parmesan panko mixture, pressing down gently so the crumbs adhere.

Bake at 400°F (200°C) for 15 to 18 minutes, until mushroom caps are tender, the cheese filling is bubbling hot, and the panko crowns are deeply golden-brown and crispy. Transfer to a serving platter, garnish with chopped fresh parsley, and serve piping hot!