Preheat oven to 350. Spray a 9-inch cast iron skillet with cooking spray.
In a large bowl cream together butter and sugars. Add vanilla and eggs and mix til smooth. Mix in flour and cocoa powder. Gently stir in white chocolate chips. Spread batter evenly into prepared pan (don't over-fill!).
Bake 25-30 minutes or until an inserted toothpick comes out clean. Remove from oven and allow to cool slightly before serving. Top with vanilla ice cream if desired. Enjoy!
Notes
Serve slightly warm, topped with vanilla ice cream and caramel sauce for the ultimate treat!