Mix ingredients together in a blender (except the bitters).
Pour into a highball glass and stir with a cinnamon stick.
Leave refrigerated for an hour or longer.
Pour into another glass topped with ice and add a dash of bitters.
Garnish if desired.
A jug makes 4-5 servings dependent on the shape of the jug.
Multiply accordingly on the amount of thirsty guests you have.