It's impossible to have a well-stocked bar without orange liqueur. Except we rarely call it orange liqueur. We call it curaçao, or triple sec, or by one of its proper names: Cointreau, Grand Marnier. Online cocktail forums are full of some serious Kirk-vs-Picard level of nerd arguments about the differences between the liqueurs. (If you're interested in a deep dive into the distinctions, check out this Serious Eats guide.)
Orange Liqueurs to Buy
Orange liqueur, in one form or another, is easy to find at any liquor store. Most are clear and based on a neutral spirit, including Cointreau, Patron Citronge, and Luxardo Triplum; Grand Marnier, made partially from a Cognac base, is richer and carries the unmistakable flavor of the grape brandy. The less-pricey brands tend to taste overly sweet with a harsh bite. They taste, in a word, cheap.
Should I Make My Own Orange Liqueur?
When mixing drinks, I tend to prefer Grand Marnier in cocktails with aged spirits and Cointreau in drinks made with clear spirits. Neither of them is out-of-this-world expensive, but keeping both on hand costs about $60. I've found that I'm a little wary of "wasting" either in untested recipes. I tried keeping the cheap stuff on hand as a back-up, but that just resulted in gross drinks.
DIY orange liqueur saves a little cash, but more importantly, its flavor profile is a good match for a wide variety of spirits and cocktail ingredients. The mix of navel and bitter orange peels along with brandy and vodka gives it a flexible, sweet-but-not-too-sweet flavor that makes for well-balanced cocktails. It isn't as refined as Grand Marnier or Cointreau, but it comes close enough that I'm happy to use it in my Sidecar or Cosmopolitan as well as in more experimental concoctions.
A side-by-side comparison of homemade orange liqueur with a bottom-shelf triple sec is no contest: DIY wins it by a mile. If you're feeling adventurous, mix up a special batch with some extra spices or flavorings. I made a batch with cinnamon and cloves that pairs well with rum and whiskey, and I think vanilla could make for a fun addition, too.
It would be quicker to list cocktails that don't contain orange liqueur than to list the ones that do. This stuff really is essential, and you'll see it in a wide variety of drinks from sours like the Margarita and the Derby to fruity fare like the Lusty Red Sangria.
Orange liqueur pairs well with Cognac or rye, like in the Morning Glory. You can even keep warm with Orange Pisco Hot Chocolate and Mulled Apple Cider. It's also a great addition to crepes, chocolate mousse, cheesecake, and biscotti. You may find yourself making orange liqueur by the gallon once you see how useful it is.