Add the ice cubes to your blender, ensuring they're evenly distributed on the bottom.
Sift in the cocoa powder and sprinkle the sugar over the ice to help dissolve later.
Add the vanilla extract to the mixture for aromatic richness.
Pour in the milk, which will help the blender blend everything smoothly and create a creamy texture.
Blend on high speed until the mixture is thick, slushy, and the ice is finely crushed — about 30-45 seconds, with a loud blending sound and a frosty appearance.
Stop the blender and check the consistency: it should be smooth yet icy, holding together when you scoop it with a spoon.
Spoon the chocolate slushie into chilled glasses for a frost-kissed presentation.
Top generously with whipped cream for a luscious finish and extra visual appeal.
Serve immediately with a straw or spoon, enjoying the cool, chocolatey goodness.