Combine corn puffs and peanuts in a large roasting pan.
Bring butter, brown sugar, and corn syrup to a boil in a heavy 2-quart saucepan. Cook and stir for 2 minutes. Remove from heat; stir in baking soda until mixture foams up. Pour over corn-peanut mixture and toss well using rubber spatulas.
Bake in the preheated oven, stirring every 10 to 15 minutes, until a cooled piece of corn is crunchy, about 45 minutes.
Spread on waxed paper to cool. Break apart and transfer to an airtight container.
