Oleo Saccharum

Yields: A concentrated citrus-oil syrup | 3–24 hour rest

Ingredients

Peels of 6 Lemons (or oranges, grapefruit, lime — pith minimized)
Sugar — start with 2 heaping tbsp for a traditional punch slurry (Educated Barfly), or use ½–1 cup if you want more liquid syrup for cocktails
Optional: A splash of hot water or fresh citrus juice to dissolve leftover sugar crystals after resting

Instructions

Peel carefully: Use a sharp peeler. Take wide strips of zest and leave as much white pith behind as you can — pith = bitterness.
Muddle: Put peels in a bowl. Cover with sugar. Muddle 3–5 minutes until the sugar clumps and looks wet with citrus oil. Switch hands. It is a workout.
Rest: Cover tightly. Refrigerate at least 3 hours; 24 hours is better. Sugar keeps pulling oil and moisture from the peels into a fragrant syrupy sludge.
Use: For punch, build the bowl on top of the oleo and peels, then strain. For bottled syrup, strain off the liquid (press peels), add a little water or juice if crystals remain, and refrigerate.

Source: Technique adapted from The Educated Barfly — How to make Oleo Saccharum. This is citrus flavor without juice acidity — “three-dimensional” peel oil for punches, lemonade upgrades, and stirred drinks. Try orange oleo in an Old Fashioned instead of plain sugar. For lasting lemon/lime juice (acids + peel oils), see Citrus Super Juice.