Combine all ingredients in a blender and blend until smooth and frothy.
Pour into glasses and dust lightly with ground coffee, if you desired.
For an extra cold drink, pour iced coffee into glasses filled with more ice—ideally, coffee ice cubes for stronger coffee flavor. To make coffee ice cubes, brew 1 1/2 teaspoon coffee in 1 cup hot water, add sugar to taste. Freeze in ice-cube tray.