Russian Water (Vodka)
The perfect cosmo is made from vodka. Some claim that vodka, dating back to 1405, is the Russian diminutive for water (voda); thus Russian water.
Vodka is principally made from wheat or rye, though the Russians did figure out how to make a great tasting distillation from potatoes.
Sadly, or happily depending on your perspective, the best Russian water is made in France. Just as the Japanese took the French chef's knife and produced the far superior Santoku knife, the French took Russian Water to the next level and created Grey Goose (specifically for the American palate.)
The best Grey Goose vodka with which to make the perfect cosmopolitan is Grey Goose L'Orange. Infused with the essence of Florida (yes, American) oranges, this distilled beverage is the foundation of the perfect cosmo.