First, preheat the oven to 375°F (190°C). Next, line a baking sheet with parchment paper or lightly grease it with cooking spray. Then, gather all ingredients and tools to ensure smooth preparation.

Begin by gently wiping each mushroom with a damp paper towel to remove any dirt. Importantly, avoid soaking mushrooms in water, as they absorb liquid quickly and become soggy. Carefully twist off the stems, creating a hollow cavity in each cap. Subsequently, chop the mushroom stems finely and set them aside for the filling.

In a large skillet, melt the butter over medium heat until it begins to sizzle. Add the minced garlic and chopped mushroom stems to the pan. Cook for approximately 4-5 minutes, stirring occasionally, until the stems are softened and most moisture has been released. Remove the skillet from heat and allow the mixture to cool slightly.

Meanwhile, in a medium mixing bowl, combine the softened cream cheese, ¾ cup of Parmesan cheese, dried thyme, onion powder, black pepper, cayenne pepper, salt, and fresh parsley. Add the cooled mushroom stem mixture to the bowl. Mix everything together thoroughly until a smooth, creamy filling is achieved. The consistency should be spreadable but not runny.

Using a small spoon or a piping bag with the corner snipped off, generously fill each mushroom cap with the cream cheese mixture. Pack the filling firmly into the cavity and allow it to mound slightly over the top. This extra filling creates a beautiful presentation and ensures every bite is packed with flavor.

Sprinkle the remaining ¼ cup of grated Parmesan cheese over the stuffed mushrooms. If desired, press each stuffed mushroom, filling-side-down, into the optional panko-butter mixture for an extra crispy topping. Arrange all stuffed mushrooms on the prepared baking sheet in a single layer with slight spacing between them.

Place the baking sheet in the preheated oven and bake for 18-20 minutes. The mushrooms are ready when they’re tender, the filling is bubbling, and the tops are golden brown. For an extra crispy, golden finish, turn on the broiler for the final 1-2 minutes, watching carefully to prevent burning.

Remove the stuffed mushrooms from the oven and let them rest for 5 minutes before serving. This cooling period prevents burning mouths and allows the flavors to settle. Garnish with additional fresh parsley and serve warm on a decorative platter.