Pour your 5 cups of chex mix in a large bowl. Melt your white chocolate in a microwave safe bowl in 30 second increments until fully melted or by following the directions on the package. Pour melted chocolate over cereal and mix until all is covered. Fold in the crushed candy canes. In a large ziploc bag or container, add the powdered sugar and chocolate covered cereal. Seal the ziploc bag or container and shake until cereal is covered with powdered sugar. Throw away excess powder. Store at room temperature.