- Add the milk, cocoa powder, sugar, chili powder, vanilla extract (if using), and ice cubes into the blender. 
- Secure the lid on the blender and blend on high speed until the mixture is smooth, thick, and frosty, about 30-40 seconds. 
- Stop the blender and check the texture; if it’s too thick, add a splash more milk and pulse a few times to loosen. 
- Pour the slushie into chilled glasses, allowing the icy texture to settle for a few seconds. 
- Garnish with a sprinkle of chili powder or a dollop of whipped cream for presentation, if desired. 
- Serve immediately with a straw and enjoy the cool, spicy chocolate flavor.