Pour the espresso into a mug.
Place the milk in a wide glass orglass jar and microwave for 30 seconds until it is very hot but not boiling.Alternatively, heat the milk in a saucepan over medium heat for about 5 minutesuntil very hot but not boiling, watching it carefully.
Add the caramel sauce and sugar (if using) tothe hot milk and stir until they dissolve.
Using a milk frother, froth themilk until you don’t see any bubbles and you have a thick froth, 20 to 30seconds. Swirl the glass and lightly tap it on the counter repeatedly to popthe larger bubbles. Repeat this step as needed.
Using a spoon to hold back the foam, pour themilk into the espresso. Spoon the remaining foam on top.
Drizzle the top with more caramelsauce.