Prepare the jars by washing them well and sterilise by drying them in a 150°C for 10 minutes.
Rinse off the mint leaves, and place them into a large saucepan.
Bruise the leaves by pressing down with the bottom of a jar or glass.
Add the water, and bring the mint to a boil. Remove from the heat, cover, and allow to stand for 10 minutes for the mint to infuse.
Stir in the vinegar. Mix in the sugar and cook over a low heat until the sugar dissolves. You can feel the sugar on the bottom of the pan like sand.
Bring to a rolling boil and boil for exactly 1 minute. Use a kitchen timer.
Remove from the heat, and skim the foam off the top using a large metal spoon.
Strain the jelly through a cloth lined colander. Discard the mint leaves.
Transfer the jelly to hot sterilised jars, and seal.
Once completely cooled, label and date.
Refrigerate after opening.
