Place Puffcorn curls and peanuts in a large roasting pan; set aside. In a large heavy saucepan, bring the butter, brown sugar and corn syrup to a boil, stirring occasionally; cook for 2 minutes. Remove from the heat and add baking soda; stir well (mixture will foam up). Pour over corn curl mixture and toss well to coat.
Bake at 250° for 45 minutes, stirring every 15 minutes. Spread on waxed paper to cool. Break apart and store in airtight containers. Yield: 5 quarts.