So this was something of an experiment on my part. What would happen if I made a Basil infusion? So I'm going to break with my previous format and more describe what happened, because it's not exactly what I expected. First I took a ball jar, lightly packed it with organic rinsed and dried basil. It wasn't packed tightly, but filled to the top with fresh leaves. Then I covered the leaves in rum. I watched the color and after a couple days I tried the infusion and it was nice, but entirely too weak. So after a week I tried it again and it was grotesque. Given the quality of the earlier flavor I decided that I just needed to change my approach.
So this time I started another jar of basil and checked it each day. As soon as I saw the leaves start to break down I took them out and replaced them with a batch of fresh leaves. After two infusions of the same alcohol I had a finished product that was both flavorful enough and tasted like basil and not the bottom of an alcoholic compost heap. When you opened the jar it smelled almost like marinara sauce. A few people at the first liqueur class thought the same.
What is so delightful about the basil infusion is that it mixes with so many different flavors. It blends very well with fruit, much like a light basil chiffonade in a melon salad. At the same time the herbal notes bring a delightful brightness to a gin martini.
It's a very different approach to the sort of flavor palette than most people think of when they think of possible infusions and the flavor honestly is too odd in the mouth to be the main element of a liqueur in my opinion, but a splash of it is an amazing accent to many other flavors. It does mix well with sweet notes and I would recommend white sugar syrup for using it in sweet liqueurs. That said an unsweetened infusion might be best for a dry martini or other similar applications.