What is oleo-saccharum? First, let's dissect the word itself. Oleo—oil or fat. Saccharum—sugar. So literally, the word itself simply means oily sugar, or perhaps more appetizingly, sugared oil.
Oleo-saccharum is an ingredient in cocktails and punches that was relatively commonly used in 19th-century bartending as a way to provide an elegantly citrusy flavor and aroma to alcoholic beverages. (For more about the history and use, I recommend David Wondrich's recent book, Punch.)
How do you make this elixir? It's simple, really.
First, zest a few lemons, leaving behind most of the white pith. I find that a vegetable peeler is the best tool for this job.
Add sugar. White is easiest to use because it will dissolve quickly when you're ready to mix the oleo-saccharum into a punch or other beverage. Wondrich calls for 2 ounces sugar for each lemon's worth of peel. So if you peel 4 lemons, use 8 ounces sugar. Honestly, though, I usually just eyeball this.
I like to use my hands at this point to gently toss the sugar into the peels. Then, using a muddler or a heavy wooden spoon, pound the lemon peels and sugar until the peels begin to express their oils. Walk away from it for at least half an hour. An hour would be better.
After an hour, you'll have a bunch of lemon peels in the bowl, but a nice amount of lemon oil also, pooled up in the bottom of the bowl.
You don't need to drain the oil off the peels, but if you did, it would look something like this:
What you do with it at this point is up to you. You can certainly use it in punch, and your loved ones will rightly deem you a hero and inspiration. Equally lovely, though, is to use it as a basis for lemonade. With a pregnant wife at home, I've done this a lot this summer, to give her something to enjoy while I crassly toss back martinis, daiquiris, and other boozy treats.
What I like to do is to take the contents of my bowl—lemon peels, oil, undissolved sugar, and all—and add them to a small saucepan. I pour on a bit of water, usually around a cup. I bring that to a quick simmer, stirring to dissolve the sugar. I remove it from the heat, and when it's cool, I strain it into a measuring cup and then discard the peels. This becomes the syrup for my lemonade.
I take the denuded lemons, juice them, and add that to a bottle along with the syrup. I shake that up really well to make a lemonade concentrate; when I'm ready to serve, I pour the concentrate into an ice-filled glass, and top it off with seltzer from a siphon. Huzzah! Sparkling lemonade, rich with luscious lemon oils.
Other alcohol-free uses include adding it as a sweetener for iced tea, as an ingredient in vinaigrette, or as an ice-cream topping. Oleo-saccharum is so versatile, in fact, that it deserves to occupy a much wider place in a home cook's arsenal of techniques.