Spray a 9x12-inch glass baking dish with cooking spray.

Use an additional baking dish if needed.

Drizzle olive oil or butter in the bottom of the baking dish.

Wipe mushrooms with a damp paper towel to clean.

Remove stems, set aside caps and chop stems to add to filling.

In a medium bowl, mix crabmeat, chopped mushroom stems, onion, dry mustard, 1 cup parmesan cheese, bread crumbs, parsley, red and black pepper, and garlic salt.

Mix well and then stir in egg and mayonnaise.

Use a small cookie scoop to mound filling onto each mushroom cap.

Melt butter and mix in garlic salt and drizzle over the filled mushrooms.

Mound a generous portion of the shredded parmesan cheese on top of each filled mushroom. Note: For softer, melted cheese, you may want to use mozzarella cheese or brick cheese for the topping.

Bake for 20 to 25 minutes at 425°F.