So somehow I missed doing a blog post on coffee flavored infusions back when that was my focus. Someone asked me for the recipe for a coffee liqueur I did for a party a couple months ago and I figured I'd point them to my blog post . . . NO BLOG POST!!! So here we go.
Coffee is a classic infusion flavor. It is bright, brings some caffeine to the party, though in more natural quantities than those hopped up alcoholic energy drinks (shudder), and is among the most classic of flavors. It's earthy, deep, slightly bitter, yet incredibly smooth when carefully balanced. Unlike most other ingredients I've posted about there is quite a bit of complication in choosing your source ingredients. Ginger is more or less ginger, blueberries are more or less blueberries and so on and so forth. Certainly quality varies, but for the most part you either have "great fruit" or "mediocre fruit". Coffee on the other hand comes in myriad varieties and beyond the basic quality concerns of freshness there is roast preference, the type of beans you prefer, how ground you want your beans to be, etc. etc. Really it's all the same variables that go into a great cup of coffee, only applied to alcohol extraction instead of water extraction. There is no "best bean" you will need to experiment a bit to find out what you like the most. That said here are the things I recommend:
Go Dark: I like my coffee fairly nutty, but I like my coffee infusion to be fairly dark. The alcohol doesn't take out much of the carbon bitterness of dark coffee, but it does take out the carmelization in the bean's sugars and the complex flavors that develop. I've made some delicious liqueur from Turkish and espresso coffee. That said a more moderate if still somewhat dark full city roast might bring a set of flavors to the party that you prefer. As with all things, experiment.
Go Fresh: This I cannot emphasize enough. Coffee gets stale over time, and depending on the nature of the coffee that time can be very brief indeed. At one point, just to see if it would work I got the leftover espresso grounds from a local coffee shop and made liqueur out of them. To explain what this is about, when you make a GOOD shot of espresso you overload your mechanism and then pack everything down. This results in some of the grounds falling out. It's just part of pulling a good shot. Some techniques waste more or less coffee, but they all waste some grounds. The liqueur I made tasted delicious, but for the first couple months of it's existence it smelled a bit like the garbage can. I couldn't figure it out, but it was very disconcerting. I do know that when coffee is ground that fine, and left out exposed to the air it goes stale very very quickly, and I've never had a similar effect with fresh coffee. So go fresh, and avoid the smell of compost in your liqueur.
Ratios: I recommend about a cup of grounds to a 5th of liquor, though to be honest I rarely measure, so that is a very rough estimate. You can't really let this infuse too long. The joy of a cold alcohol infusion in coffee is it doesn't bring out all those unpleasant volatile bitter compounds that you find in a hot brew of the bean.
Flavor Profile: We've all had coffee. This will be a somewhat less round version of the flavor, and much less bitter that a hot brew. It can be slightly nutty, very deep, and excellent with all things cream, much like a normal cup of Joe. The most traditional flavor to go with coffee liqueur is probably vanilla. Kahlua is coffee and vanilla. It's a sure fire hit. Other good flavors are cacao, cinnamon, cardamom (hmmm Turkish Liqueur), and really any deep earthy spice. As always experiment and see what strikes your fancy.