Mixologist

miksologi A person who creates cocktails; a bartender.
1999, Bob Emmons, The Book of Gins and Vodkas: A Complete Guide, p. 63.

By the way, the difference between a bartender and a mixologist can be confusing, but normally a bartender serves the patrons at a sit-down style bar, where a mixologist would usually work at a very busy service-style bar.