Chill a coupe glass.
Combine gin, Campari, triple sec, lemon juice, and rich sugar syrup in a shaker.
Add ice and shake hard for 10–12 seconds.
Fine-strain into the chilled coupe.
Express a lemon zest twist over the surface to release the oils, then drape or balance it on the rim as garnish.
Paul Harrington developed this drink at the Townhouse Bar in Emeryville, California, in the mid-1990s; the 2:1:1:3 ratio (gin heavy, citrus generous) is intentionally tart, so the optional sugar syrup is a genuine balancing tool rather than an afterthought - adjust to taste.
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