It's called green dragon.
There are two methods for extracting the cannabinoids from the buds. The first involves heating the alcohol to improve its power as a solvent. The cannabis buds are stewed in about 25cl of spirit, preferably heated in a water bath to reduce the possibility (probability, in the case of heating high-proof alcohols such as Everclear) of ignition of the alcohol vapours. The temperature of the spirit should be maintained below the boiling point of ethanol (78.4º C)(173ºF) to prevent the buildup of fumes. The majority of the soluble cannabinoids will be extracted by this method after about 20 minutes of heating.
The second method, which is considerably more low-tech, involves leaving cannabis buds, leaves, and stems in the spirit for several weeks or months. Over time the cannabinoids will leach from the plant matter in much the same way as in the heating method. It is common to simply open a new bottle of spirit, poke several cannabis buds into the bottle (it may be necessary to pour off or drink some of the spirit first) and reseal. The bottle must be kept tightly sealed to prevent the alcohol evaporating from the spirit. The bottle must be kept in a dark place because tetrahydrocannabinol decomposes under the influence of light.
Courtesy of Wikipedia