Prep the Glassware: Place a sturdy rocks glass in the freezer for about 10 minutes to chill before serving.
Combine Liqueurs: Fill a mixing glass with plenty of solid, high-quality ice. Pour in exactly 1 ounce of gin, 1 ounce of sweet vermouth, and 1 ounce of Campari.
Stir to Chill: Stir the mixture smoothly using a bar spoon for about 20 to 30 seconds until the mixing glass feels thoroughly frosted on the outside. (Do not shake to avoid dilution).
Strain and Pour: Place a single large, dense ice cube into your chilled rocks glass. Strain the liquid directly over the ice cube.
Garnish & Serve: Express the essential oils of a fresh orange peel over the surface of the glass, drop the peel into the drink, and serve immediately.