Preheat oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper. Wipe baby bella mushrooms clean with a damp paper towel. Gently snap off stems; finely mince ½ cup of the stems and discard or save the rest for vegetable stock.

Brush mushroom caps lightly on both sides with olive oil, sprinkle with sea salt, and arrange cavity-side up on the prepared baking sheet.

In a small skillet, heat 1 teaspoon of olive oil over medium heat. Sauté the minced mushroom stems and minced garlic for 2 to 3 minutes until softened and fragrant. Remove from heat and allow to cool slightly.

In a mixing bowl, combine softened cream cheese, sautéed garlic-mushroom mixture, ⅓ cup grated Parmesan, chopped fresh parsley, fresh thyme, onion powder, and black pepper. Stir vigorously with a spatula until smooth and creamy.

Using a small spoon or cookie scoop, mound generous portions of the cream cheese filling into each hollowed mushroom cavity, smoothing slightly on top.

In a small bowl, toss panko breadcrumbs with melted butter and the remaining 2 tablespoons of grated Parmesan. Spoon or press the buttery panko crumbs over the cream cheese filling on each mushroom.

Bake uncovered at 400°F for 18 to 20 minutes until the mushroom caps are tender and juicy, the filling is piping hot, and the panko tops are deeply golden and crisp. Garnish with fresh parsley and serve warm!