- In a blender, combine the milk, heavy cream, chocolate syrup, powdered sugar, vanilla extract, and ice cubes. 
- Blend on high speed until the mixture is smooth and frothy, about 30-45 seconds. 
- Taste the mixture and adjust sweetness if desired by adding more powdered sugar or chocolate syrup. 
- Pour the frozen hot chocolate into serving glasses. 
- Top each glass with a generous dollop of whipped cream. 
- Garnish with chocolate shavings or mini marshmallows for an extra treat. 
- Serve immediately with a straw or spoon.