Bring milk to a gentle simmer either on the stovetop or in the microwave.
In a heat-proof measuring cup, whisk together sugar and cocoa powder until there are as few lumps as possible.
Chop or break chocolate into chocolate-chip-sized pieces. Chocolate chips may also be used, but make sure they are high quality baking chocolate, otherwise tragic events may occur.
Pour hot milk over sugar and cocoa mixture. Stir until smooth.
Add chocolate and wait for about 2 minutes while chocolate melts. Stir until smooth. For extra smoothness and frothiness, blend with an immersion blender for about 30 seconds.
Pour into a 10-ounce mug and serve immediately. For additional servings, just scale the ingredients up by the number of servings needed.
