Arrange bread slices in a 13x9-in. dish. In a small bowl, combine sugar, cocoa, salt and baking powder. In another bowl, whisk eggs, milk and vanilla. Gradually whisk into dry ingredients until smooth. Pour over bread. Let stand 10 minutes, turning once.
In a large skillet, melt butter over medium heat. Cook bread for 3-4 minutes each side or until toasted. Serve with toppings of your choice.