Preheat Oven: Preheat your oven to 350°F (175°C).
Prepare Mushroom Caps: Clean the mushrooms with a damp cloth and remove the stems. Set the caps aside on a baking sheet lined with parchment paper. Finely chop the mushroom stems.
Sauté the Stems: In a sauté pan over medium heat, melt the butter. Add the chopped mushroom stems and garlic. Sauté for about 5 minutes, or until the mixture becomes soft and fragrant. Remove from heat.
Make the Stuffing: In a mixing bowl, combine the sautéed mushroom stems, cream cheese, Longhorn cheese, breadcrumbs, fresh parsley, thyme, salt, and pepper. Mix until everything is well combined.
Stuff the Mushrooms: Spoon the stuffing mixture into the mushroom caps, pressing gently to ensure the filling stays in place. Optionally, sprinkle with Parmesan cheese for an extra golden topping.
Bake: Place the stuffed mushrooms in the oven and bake for about 20 minutes, or until the mushrooms are tender and the stuffing is golden brown.
Serve: Once done, remove from the oven and let cool for a few minutes. Serve warm as an appetizer or side dish!
