Preheat oven to 250 degrees F (120 degrees C). Lightly grease a large roasting pan.
In a large bowl, mix crispy corn and rice cereal, slivered almonds and toasted, chopped pecans.
In a medium saucepan over medium heat, melt the butter and mix with dark corn syrup and light brown sugar. Pour the mixture over the crispy corn and rice cereal mixture. Stir and shake to coat all the nuts and cereal.
Pour the coated mixture into the prepared roasting pan. Stirring approximately every 15 minutes, cook 1 hour in the preheated oven. Cool on wax paper, and store in airtight containers.