I must make 50 batches of this during the year. My friends now call it "Crack" as it is addicting. Another called it "Meth" when he got some while it was warm out of the oven. I make this during the holidays and after the mix has cooled, I add candy corn to add some fun color to it. If you want a sweet and salty mix add pretzel sticks. It's also good drizzled with chocolate.
Line two 15 x 10 inch baking pans with No Stick Foil (or spray with no stick spray); set aside. In large heatproof bowl, combine the cereal, set aside.
In a heavy saucepan over medium heat, bring butter, brown sugar and corn syrup to a boil, stirring constantly. Reduce heat. Simmer, uncovered for 5 minutes, stirring occasionally. Remove from heat; stir in vanilla. Pour over cereal and stir until well coated.
Transfer to prepared pans. Bake, uncovered, at 200 degrees for 1 hour, stirring every 15 minutes. Cool completely. Break apart and store in airtight containers. Yields 4 1/2 quarts