Brew 2 shots of espresso (about 60 ml). If you do not have an espresso machine, prepare 60 ml of very strong brewed coffee. Keep it hot and set aside.

Chocolate

In a small heatproof cup, combine 2 tsp unsweetened cocoa powder and 1 tsp granulated sugar. Add 1 tbsp hot water and whisk until smooth and free of lumps, forming a thick chocolate syrup. If using 15 g finely chopped semisweet chocolate, add it to the hot chocolate syrup and stir until melted and fully incorporated.

Milk and foam

Heat 250 ml milk in a small saucepan over medium heat until it reaches about 60–65°C (steaming but not boiling). If using vanilla extract, stir in 1 tsp now. Alternatively, microwave milk in a microwave-safe pitcher until hot (about 1–1.5 minutes depending on microwave).

Froth the hot milk using a milk frother, steam wand, or handheld whisk until it develops microfoam. If you have no frother, vigorously whisk or shake the hot milk in a tightly sealed jar for 30–45 seconds.

Assembly

Pour the chocolate syrup into a 12-16 oz (350–475 ml) mug. Pour the 2 shots of hot espresso over the chocolate and stir to combine thoroughly, creating the mocha base.

Pour the steamed milk into the mug, holding back foam with a spoon. Spoon the remaining foam on top.

If desired, whip 30 ml heavy cream lightly (or use prepared whipped cream) and dollop on top of the foam.

Garnish

Sprinkle 1 tsp cocoa powder or chocolate shavings over the foam or whipped cream. Add mini marshmallows if using.

Serve immediately with a spoon or straw.