Prepare the margarita glasses.
Put some salt on a saucer.
Wet the rim of the glasses with lemon or lime juice (note to self: take photos of this procedure for a “how to” post).
Dip the rim of the glasses in the salt.
Put all the ingredients in the blender. Add crushed ice, if you like.
Pulse two to three times to blend and to break the mint leaves into smithereens.
Pour into the prepared glasses and serve at once.