To a medium microwave-safe bowl, add the butter, honey, vanilla, and cinnamon. Microwave in 30-sec. intervals until butter melts. Stir to combine, then add to a slow cooker.
Add Goldfish, honey nut cereal, and cashews to slow cooker. Toss until well coated. Cover, leaving lid slightly ajar to let steam escape, and cook on high 1 hour, stirring every 15 min.
Line a large baking sheet with wax paper. Transfer mixture to baking sheet and add cranberries, tossing to combine. Spread out in single layer and let cool completely. Store in airtight container up to 1 week.