Using a wet paper towel, wipe off any dirt from mushrooms. Cut off stems from mushrooms and dice into small pieces.
In a medium skillet over medium heat add 1 TBS cooking oil and heat up. Add in diced onion and diced mushroom stems. Cook for 2 minutes. Stir in minced garlic and cook for 30 seconds. Season with salt & pepper. Turn off heat. Add in cream cheese and stir until melted & combined. Place mixture into a medium bowl.
Place crab meat onto a plate. Sort through & pick out any shells. Place crab meat into bowl of mixture. Mix in 2 TBS fresh chopped parsley, egg, 1/2 cup parmesan cheese, 1/4 cup bread crumbs, and 1 TBS dried chives, to combine.
Spray a 9 x 13 baking dish with non-stick cooking spray. Place mushrooms cap side down in baking dish. Brush melted butter all over mushrooms. Place mixture into mushrooms mounding at the top.
Top with additional parmesan cheese.
Bake in a 375 degree preheated oven for 20-25 minutes. Garnish with additional fresh chopped parsley