While not exactly underrated, bitters can sometimes be overlooked in modern cocktails. A few dashes of aromatic or flavored bitters can elevate the complexity of your drink. Experiment with different types, such as Angostura, Peychaud's, or orange bitters.
This less refined, golden-brown sugar has a rich, molasses-like flavor that can add depth to your old-fashioned. Its coarse texture also gives a nice texture to the cocktail.
Absinthe was once banned in several countries but has experienced a revival. Adding a small amount to your old-fashioned can provide a subtle anise flavor and a touch of mystique.
While orange zest is commonly used, consider using a larger piece of orange peel with some of the pith (the white part). It can contribute a bitter and aromatic element that complements the sweetness of the cocktail.
Cherry Heering is a Danish cherry liqueur that adds a rich, dark cherry flavor to cocktails. It can be a delightful substitution for the standard maraschino cherry in your old-fashioned.
Instead of the usual simple syrup, try using maple syrup for a nuanced sweetness. It brings a warm, earthy flavor that pairs well with the depth of bourbon or rye.
Also known as pimento dram, this liqueur is made from allspice berries. Adding a small amount can impart warm, spicy, and slightly sweet notes to your old-fashioned.
While not exactly underrated, rye whiskey is sometimes overshadowed by its sweeter cousin, bourbon. Rye's spicier and drier profile can bring a different dimension to your old-fashioned.