If you have loads of feral mint taking over any patch of your plot, here is a good use for it. Use it in cold water or soda water, or in cocktail (I think a dash in a Mojito would be lovely). This makes roughly 1.5 litres.
300g fresh mint, washed, which is basically several big bunches
1 litre of water
1.2kg sugar
(Yes you can reduce or increase quantities proportionally).
Chop up the stems of mint roughly and bruise it.
Boil the water and pour over the mint in a bowl, and steep the mint in the water for 24 hours, covered.
The next day, wring out the mint getting all the drops of juice out.
Dissolve the sugar into it then boil for 2-3 minutes.
Cool and bottle.