Pull two shots of fresh espresso (about 2 oz). If you don’t have an espresso machine, brew 2 oz very strong coffee. Keep it hot. Measure and set aside 1/4 cup hot strong brewed coffee to extend the drink to 12 oz total volume.

Stir the coffee syrup (or simple syrup) and optional dark rum/coffee liqueur into the hot espresso until dissolved.

Mascarpone Cocoa Mixture

In a small bowl, combine the room-temperature mascarpone, granulated sugar, unsweetened cocoa powder, and vanilla extract. Whisk vigorously until smooth and slightly loose — you want a pourable cream, not stiff. If too thick, add a very small splash (1/2 tsp) of hot espresso and whisk to loosen.

Taste and adjust sweetness or cocoa: add up to 1/4 tsp more sugar or cocoa to balance, then set aside.

Milk & Foam

Warm the whole milk and heavy cream together in a small saucepan over medium-low heat until steaming but not boiling (about 150–155°F / 65–68°C). Alternatively, use a milk steamer. Do not scald.

Froth the warmed milk/cream until you have a velvety microfoam with small, fine bubbles. Use a steam wand, handheld milk frother, or immersion blender (whisk briskly) for 20–30 seconds to create foam.

Assembly

Preheat a 12-oz mug by rinsing with hot water, then discard water. Pour the espresso + coffee + syrup mixture into the mug.

Spoon the mascarpone cocoa mixture into the hot coffee and stir briskly until mostly incorporated. The heat will slightly melt the mascarpone creating a creamy tiramisu flavor.

Slowly pour the steamed milk into the mug, holding back the foam with a spoon. Aim to leave about 1/2–3/4 inch of foam on top.

Spoon the remaining foam on top to create a cappuccino-style crown. If desired, gently swirl the remaining mascarpone mixture on top for a marbled effect.

Garnish & Serve

Dust the top lightly with the 1/2 tsp unsweetened cocoa powder using a fine mesh sieve for an even layer.

Sprinkle chocolate shavings if using. Serve immediately while hot.