Preheat oven to 425 degrees F. Pray a 9" x 13" baking dish with cooking spray and spread 2 tablespoons of butter on the bottom of the pan. Set aside.
Remove the stems from the mushrooms and cut up 6 stems to add to the filling.
In a medium bowl, mix crabmeat, mushrooms stems, onion, cheeses, parsley, peppers and garlic salt. Mix to combine and then stir in egg and yogurt.
Place the mushrooms into the prepared baking dish and use a small ice cream scoop (or measure out 2 tablespoons) to mound the crab mixture. Place in the center of each mushroom cap.
Melt the butter and garlic salt together and drizzle over the crab stuffed mushrooms. Top with additional shredded cheddar cheese and bake for 25-30 minuts. Garnsish with parsley (optional) and serve. Enjoy!