1. Place puffed wheat in a large bowl, and set aside. Grease one 9×9 inch pan.
2. Grease the rim of a medium saucepan to prevent boil-over. Place the cocoa powder, corn syrup, brown sugar, and butter or margarine in the saucepan. Cook over medium heat, stirring often until mixture comes to a full boil. Allow to boil for 1 minute, and then remove from heat.
3. Pour chocolate mixture over puffed wheat, and stir until puffed wheat is evenly coated. Using a buttered spatula, press mixture into the prepared pan. Allow to cool, then cut as desired. Wrap squares individually, or store in an airtight container