Absinthe is a liqueur distilled from wormwood, an extremely bitter tasting plant, and flavored with a variety of herbs. Traditionally it was proofed very strong, at 136 proof (or around 68% alcohol), and is legendary in history for inspiring such famous artists as Van Gogh or writers like Hemingway. (It is unproven that Van Gogh cut his ear off because of Absinthe, but he was a renowned consumer of the potent liquid, and a manic depressive, which is never a good combination.)
The Traditional French Absinthe Ritual
Absinthe, because of it's bitterness, is traditionally served with a sugar cube. In the late 1800's and early 1900's, it was fashionable to serve the sugar cube on a flat, slotted spoon that held the sugar in place over the glass of absinthe. Water was slowly dripped on the cube, and the resulting syrup dripped through the holes in the spoon and mixed with the absinthe. As the composition of the absinthe liqueur changed, the alcohol percentage dropped, forcing the anise and other essential herbal oils to precipitate out. This caused the absinthe to take on a milky appearance, if it was made properly. (Poorly made absinthe may not show this effect. Additionally, poor absinthe often has color added to it to make it appear an unnatural emerald green.) The Modern, or "Bohemian" Absinthe Ritual
A new method of sweetening Absinthe has recently become popular. Once the absinthe is poured (now as a shot), a small amount of sugar in a spoon is dipped into the glass, soaked, and withdrawn. The sugar is then set on fire until it melts and caramelizes, and then is stirred into the drink. Cold water is then added to the drink to put out the alcohol fire.