Preheat oven to 350. In a medium bowl, hand mix flour, sugar, cocoa, salt, baking powder. Add egg, milk, melted margarine.
Stir in chocolate chips. Coarsely chop whoppers into small pieces and stir into batter. (or for the cookies without the whopper pieces, skip this step and only do the chocolate chips).
Drop tablespoon sized balls onto a prepared baking sheet. Bake for 10 minutes.
In a food processor, grind remaining whoppers into a coarse powder (It should be about the consistency of salt). Add in the cream cheese followed by the powdered sugar. Be sure to scrape the sides of the food processor so that all ingredients are evenly incorporated.
Choose two cookies of similar size and spread about 1/2 tablespoon of the filling onto one of the cookies. Sandwich the two cookies together and refrigerate until ready to consume.