Heat oven to 375. Lightly spray a rimmed baking sheet w/ cooking spray. Remove stems from 3/4 lb cleaned mushrooms. Finely chop stems and remaining mushrooms.
In lg skillet, over medium heat, melt 3 tbsp butter. Add chopped mushrooms. Cook, stirring for 5 mins. Remove from heat. Add 1/4 cup panko crumbs to mushrooms, along w/ crabmeat, onion powder, salt and pepper. Mix well.
Stuff mushrooms evenly with about 1 tsp mix. Place mushrooms on baking sheet. In small bowl, combine remaining panko crumbs and 1 tbsp melted butter. Sprinkle mix over tops of mushrooms. Sprinkle mushrooms w/ italian seasonings and paprika. Bake 15 mins or until heated through.