Preheat the oven to 350 degrees F. Line a 9X13-inch pan with foil and lightly grease with cooking spray.
In a medium microwave-safe bowl, melt the butter. Add the brown sugar and mix well. Add the eggs and vanilla and mix. Add the flour, baking powder, salt and baking soda and blend until combined.
Spread the batter in the prepared pan. Sprinkle the chocolate chips and nuts over the batter. Bake for 25-30 minutes until a toothpick inserted in the center comes out clean or with a few moist crumbs.