Grease a 9x13 inch baking pan.
Add the butter, corn syrup, brown sugar and cocoa powder to a large sauce pan over low-medium heat.
Melt everything together while stirring gently.
Bring the mixture to a gently boil for 1 minute, then remove from the heat.
Stir in the puffed wheat cereal.
Spoon the batter into the prepared pan and press down (I use a lightly greased spatula for this.
Allow to firm up at room temperature for 60 minutes, then cut into bars.
*Do not use Sugar Crisp or other puffed wheat cereals where each kernel is coated in a sugar or honey coating.
**Store bars in an airtight container at room temperature.