Measure out the milk, cocoa powder, honey, cinnamon, and cayenne, and add them to your blender.
Blend the mixture on low speed first to combine the dry cocoa and spices with the milk until smooth and no lumps remain, about 30 seconds.
Add the ice cubes to the blender, filling it up to about 1.5 cups, depending on your desired thickness.
Secure the lid and blend on high for 30-45 seconds until the mixture is thick, slushy, and smooth in texture, stopping occasionally to check consistency.
Taste the slushie and adjust sweetness if needed by adding more honey and blending again briefly.
Pour the chocolate spiced slushie into glasses, and serve immediately with a straw or spoon for scooping.