Wash the mint leave and pat dry. Remove the leaves from the stem and discard stems. Finely chop the leaves.
Start boiling the water.
Put the mint in a small container and add the water to it.
Stir in the sugar and let stand until the water is cooled off enough to touch it. This should take about 15 minutes.
Stir in the cider vinegar and sea salt.
Notes
That's it. Serve immediately or reserve to use later.This isn't in the original recipe, but you could leave the mint whole and then pulse it in a blender or a food processor after the water has cooled off.