Put Chex Mix in a large microwaveable bowl and line a large cookie sheet with foil or wax paper.
In a microwavable measuring cup add butter and microwave uncovered for 30 seconds on high or until butter is completely melted.
Add sugar and water to butter and place back in microwave for 30 seconds or until everything can be stirred smooth.
Add vanilla to butter mixture. mix and pour over cereal slowly. Be sure to stir the cereal, so it’s evenly coated.
Microwave cereal for four minutes, stop the microwave and stir every minute until it’s thoroughly glazed.
Pour powder sugar into a resealable freezer bag and shake to coat evenly. Be sure to allow cereal to cool for 1-2 minutes before placing it into the baggie.
Spread coated cereal out on your lined cookie sheet.
Melt white chocolate, if you do this in the microwave, you can place on high for 30 seconds, remove stir, and repeat stopping to stir about every 20 seconds. You don't want to burn the chocolate.
Using a food storage bag, cut off the corner, pour white chocolate into the bag and use it to drizzle white chocolate on top of the Chex mix.
Sprinkle with festive sprinkles or glitter and allow to cool about 10 minutes.