Preheat oven to 350 degrees F. Grease a 9" X 13" baking pan. Pour melted butter into a large bowl then beat in the sugars and the cocoa. Beat in eggs, and then mix in the flour and baking powder. Stir in vanilla and walnuts. Transfer batter to the pan. Bake 30-35 minutes.
To make the icing, beat cream cheese and butter until light. Beat in icing sugar. Colour icing a Halloween orange. Spread over brownie after it has cooled. Cut into bars. Top each bar with a Halloween candy.
Makes 18-24 bars depending on the size you cut them.