Tip the chocolate pieces (or hot chocolate sauce) into a 230ml heatproof cup or mug. If you don’t like your mocha too sweet, opt for cocoa powder.
Pour the espresso over the chocolate or sauce in the cup or mug. If you don’t have an espresso machine, you could use compostable coffee pods, very strong stovetop coffee, or concentrated instant coffee. Stir to melt the chocolate, if necessary, and combine it with the espresso.
Next, steam your milk. Mocha milk should be frothy and thick, and can afford to be a touch hotter than cappuccino or latte milk. If you are using an espresso machine steam wand, hold the wand just under the surface, making sure you don’t let any cold air in. It shouldn’t make any hissing noises or be spitting milk drops anywhere. Try to use steam jets to spin the milk around in a whirlpool-like motion, pulling the jug downwards slowly as the milk heats. This is called ‘stretching’ the milk, and helps produce more foam. If you have a separate steamer attachment on your bean-to-cup machine, steam the milk separately in a silver jug for pouring. You can use an electric milk frother (heat the milk first in the microwave or on the hob, making sure it doesn’t boil). Or, pour the warm milk into a French press, then carefully plunge the filter up and down to push air through the hot milk and create foam. Pour the milk into the cup and stir well to combine.
Garnish the mocha with grated chocolate or a dusting of cocoa or hot chocolate powder.