This recipe makes more ice cubes than needed for two servings of Frozen Hot Chocolate. Freeze in trays and transfer cubes to zip-top plastic bags to have on hand anytime a chocolate craving hits you.
In a small saucepan, whisk together chocolate, milk, cocoa and sugar over medium heat until chocolate is melted and sugar is dissolved, about 5 minutes. Let cool to room temperature.
Use a liquid measure or small pitcher to pour chocolate mixture evenly among two ice cube trays. Freeze, uncovered, at least 4 hours and up to 3 days. Transfer to zip-top bags and store up to 3 weeks.