Measure cereal in large microwaveable bowl. Line a cookie sheet with waxed paper or foil.
In 2-cup microwaveable measuring cup, microwave butter uncovered on High 30 seconds or until melted. Add sugar and corn syrup; microwave uncovered on High 30 seconds until mixture is heated and can be stirred smooth. Stir in vanilla. Pour over cereal, stirring until evenly coated.
Microwave uncovered on High 2 minutes, stirring after1 minute. Sprinkle with powdered sugar; mix well.
Spread on waxed paper or foil. Microwave white chocolate on High 30 seconds or until it can be stirred smooth; drizzle over top; sprinkle with edible glitter or colored candies.