1. Spray or lightly-oil a 13 x 9-inch (approx 30 x 22cm) rectangular pan.
2. In a large saucepan, melt the butter over low heat. Add the white chocolate and stir until melted.
3. Add the marshmallows and stir constantly over the heat until completely melted. (If they start to scorch on the bottom, remove from heat and continue to stir, placing the pan back on the heat occasionally, stirring until smooth.
4. Remove from heat and add the candied peanuts and Rick Krispies until well combined. A rubber spatula or flexible pastry scraper works best.
5. Scrape into the prepared pan and smooth the top. Let cool.