1. Preheat oven to 350 degrees Fahrenheit.
2. Melt butter in large skillet. Add mushrooms and turn to coat in butter. Sprinkle lightly with salt. Brown for a couple of minutes; then remove mushrooms from skillet and place in a baking dish.
3. In the same skillet, add garlic, parsley, and scallions. Sprinkle with more salt and cook for four minutes. Remove from heat.
4. Place piece of cheese inside each mushroom. Top with parsley–garlic mixture. Place pan in oven and bake for 15 minutes, or until cheese melts.