A drop or two of bitters can brighten up a whole cocktail; I particularly like grapefruit bitters in bitter, stirred cocktails. When I'm making a Negroni, for example, I always add them—grapefruit peel has a very bitter finish, so it's a perfect match with a classically bitter drink. You get a hit of citrus and a bitter backbone from just a few drops. Whether it's a stirred, spirit-forward drink or a shaken cocktail with Campari, Aperol, or Cynar, these bitters are the perfect addition.
While some of these ingredients sound obscure, gentian root and cinchona bark are essential for making these bitters, well, bitter. They're available at specialty spice stores, as are dried citrus peels, and can be purchased online as well.
2 whole grapefruits 3/4 cup dried grapefruit peel, loosely packed (about 45 grams by weight) 1 tablespoon whole coriander 2 tablespoons whole green peppercorn 1 teaspoon gentian root 1/4 teaspoon ground cinchona bark 1 whole clove 5 allspice berries 10 green cardamom pods, cracked 1 750-ml bottle Everclear®
From the whole grapefruits, cut strips of peel, avoiding the white pith as much as possible. Continue until you have removed most of the peel from each grapefruit. (Reserve the fruit for another use.) Add peels to a sealable glass jar along with all remaining ingredients. Close the lid, and gently shake several times. Let steep in a cool place out of direct sunlight for two weeks, gently shaking the jar every day or so. On the final two days, leave lid ajar to let alcohol fumes escape. Strain out the solids and return the bitters to the sealed jar. Transfer into smaller dropper jars for ease of use.