Add vodka and dry vermouth to cocktail shaker. Shake and strain into chilled cocktail or coupe glass. Use a dropper to add 3 to 4 drops of rosemary-infused olive oil. Garnish with an olive branch or fresh herb sprig.
Infused Olive Oil
Remove stems from rosemary. Add oil and rosemary to a large cast-iron pan. Heat on low for 15 minutes. Turn off heat and let it infuse for 90 minutes. Strain and funnel to a clean bottle.