Wash the mint leaves, drain, and put into a jar with the sugar and white liqueur. Let sit for about a month.

Strain the leaves with gauze or something similar. You can drink it after 2 months, but it's even better if you let it age for half a year.

You can use spearmint, peppermint, Japanese mint, or any mint you like. To sweeten, use sugar, honey, or even stevia.