Measure out all your ingredients: milk, cocoa powder, sugar, ice cubes, and vanilla extract. Place them all into the blender.
Blend on high speed until the mixture is smooth, icy, and well combined. You should see a uniform, slush-like texture with tiny ice crystals and a rich chocolate color.
Stop the blender briefly and check the consistency. If it’s too thick, add a splash more milk and blend again for a creamier texture. If it’s too thin, add a few more ice cubes and blend until desired consistency is reached.
Once the mixture is thick, frosty, and scoopable, turn off the blender. The slushie should have a granular, icy texture with no large ice chunks remaining.
Scoop the chocolate slushie into glasses or cups. The final presentation should be a vibrant, icy chocolate beverage with a slightly frosty surface.
Enjoy immediately with a spoon or straw, savoring the cool, crunchy texture and rich cocoa flavor of your homemade frozen slushie.
