On a fireproof surface like a pan or stone, light 2 sprigs of rosemary on fire until smoking or, if making these over a campfire, use tongs to hold 2 sprigs in the fire until smoking.
Invert a cocktail glass over each smoking sprig on the fireproof surface and leave the rosemary to smoke while you make the cocktails.
To a beaker, add the regular ice cubes, whiskey, vermouth, and bitters. Add a large ice cube to the beaker and stir until combined.
Take the smoked glasses, discard the charred rosemary, add an extra-large ice cube to each glass, and strain in the cocktail mixture. Run a piece of orange peel around rim of each glass, twist the peels, and add them to the cocktails. Add a fresh sprig of rosemary to each cocktail.