2 1/2 tablespoons sugar
4 1/2 teaspoons unsweetened cocoa powder, preferably Dutch process
1 1/2 cup milk,
1/4 teaspoon vanilla extract
Sprinkle of ground cinnamon
Mix sugar, cocoa and 2 tablespoons cold milk in a mug until smooth. Heat the remaining milk in a small saucepan on the stovetop or in a glass-measuring cup in the microwave until steaming hot but not boiling. Stir in the cocoa mixture and vanilla.
To froth the hot chocolate without a frothier, whirl a whisk in it by rubbing your hands back and forth. Pour it back into the mug and sprinkle with cinnamon.