Let the mint steep. Pour sugar into a bowl with mint. Pour in water, stir and leave for half an hour until the sugar dissolves completely at room temperature.
Boil the mint. Place the bowl on the fire and bring to a boil. Then reduce the heat and cook for another 10 minutes. Remove from the heat, cover with a towel and leave for 12 hours to infuse.
Cook the mint jam. Put the mint back on the fire and bring to a boil. Then leave it to infuse for 12 hours, covered with a towel. After infusing, strain the jam through cheesecloth or a fine sieve. The mint jam should be translucent.
Pour the jam into jars. Fill sterilized jars with mint jam and roll up. Store in a cool, dark place.