Combine all ingredients, mix well, and bottle in individual bottles. Serve ice cold with olives.
Note: Vermouth needs to be refrigerated after opening, and once opened will only last a couple of weeks. I recommend trying out some small batch American vermouths such as Atsby, Vya, or Imbue. Once you try them you will never go back to the cheap stuff again.
Recipe by Have You Eaten, SF? at https://haveyoueatensf.com/pre-batch-cocktails/