Fill your cocktail mixer with a couple of generous scoops of crushed ice.
Pour in the bourbon and vermouth.
Add the dashes of bitters.
Mix thoroughly with a long handled bar spoon.
Using a bar strainer, pour into a coupe glass.
A nice variation is an ounce and a half of Bourbon and a half ounce of cognac rather than 2 full ounces of Bourbon.Try other bitters such as black walnut or orange. One substitution can change the whole vibe of the drink. It may not technically be a "Manhattan," but that's okay!