Preheat oven to 250°F and line a large baking sheet with parchment paper or aluminum foil.
In a large mixing bowl, combine Crispix cereal and roasted peanuts.
In a medium saucepan over medium heat, melt butter. Stir in brown sugar and corn syrup, and bring to a boil. Let the mixture boil for 1 minute, stirring occasionally.
Remove the saucepan from heat and quickly stir in vanilla extract and baking soda. The caramel mixture will foam up.
Pour the caramel mixture over the cereal and peanuts, stirring to coat everything evenly.
Spread the coated cereal mixture onto the prepared baking sheet in an even layer.
Bake for 1 hour, stirring every 20 minutes to ensure even baking.
Once baked, let the mixture cool completely. If desired, add holiday candy for an extra festive touch. Break into pieces and serve, or store it in an airtight container.