Clean the jar by washing the jar and lid with soap or wipe the inside of jar and lid with rubbing alcohol. Dry the jar and lid, set it aside.
Wash plums by soaking them in large bowl of water for about 10 minutes. Afterwards, take them out of water and dry thoroughly.
When plums are completely dry, take a skewer and take off stem from each plum and set it aside.
In a glass jar, place layer of rock sugar at the bottom, then place layer of plums on top. Repeat the process until the jar is filled.
Pour the liquor into the glass jar and seal the lid tightly. Place jar in a cool dry place for at least 6 months. When the liqueur is ready, serve chilled on its own or on the rocks.
