If you're not already aware, cocktail bitters are aromatic infusions that are used to give mixed drinks an incredible depth of flavor. Think of them as the spice cabinet for your home bar. Many of the standard flavors - Angostura, Peychaud's - originated as tonics to settle stomachs and cure sickness.
If you're also not aware, artisinal bitters have exploded on the cocktail and home mixology scene, and all the cool kids are mixing up their own. These make an awesome weekend project, as well as a great gift to give to your friends as favors or holiday gifts.
There are countless recipes on the internet about infusing your own bitters, but I'm particularly loving this collection of recipes from America's Test Kitchen. The high alcohol-to-aromatic/spice content means they take only one to five days to mature. Plus, I love how they then provide for mixing the base bitter flavors to create custom mixes for particular cocktails, such as one of my favorite classics, the Old-Fashioned.