This is the classic Negroni cocktail, with a slight tweak: instead of using equal parts of all three ingredients, the gin is increased, making the drink less syrupy-sweet.
Add a large ice cube to the cocktail serving glass.
If you're using a cocktail mixing glass, add the gin, Campari, and vermouth and stir with a bar spoon about 30 times. Otherwise, add them all to the cocktail serving glass and stir it up to combine the ingredients.
Use a vegetable peeler to cut a large piece of orange peel, taking care not to get too much white pith on it.
orange peel
Twist the cut piece of peel over top of the serving glass with the outside part of the orange peel facing the glass. This will give it an orange aroma which really enhances the drink.
Serve immediately.
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Notes
In my version of a classic Negroni, I increased the gin and cut back a little on the Campari and sweet vermouth. This reduces the sweetness and lets the gin shine through a little more. The classic recipe, with equal parts, is delicious but a little too sweet for my palate. Try mixing up the proportions and see what you like the best!