Preheat the oven to 375°F (190°C).
In a skillet over medium heat, cook the ground beef until browned. Remove from heat and set aside.
In a medium bowl, mix together the cream cheese, Parmesan cheese, parsley, garlic, black pepper, onion powder, and salt until well combined.
Add the cook ground beef to the cream cheese mixture and stir until evenly combined.
Spoon the mixture into each mushroom cap, filling it to the top.
Place the stuffed mushrooms onto a baking sheet and bake for 15-20 minutes or until the mushrooms are tender and the cheese is melted and bubbly.
Serve warm and enjoy!