From David Lebovitz
Garnish: orange twist
Add the gin, sweet vermouth, Maraschino and orange bitters to a mixing glass.
Fill the glass partially with ice and stir the drink vigorously for 15 to 20 seconds.
Strain into a chilled cocktail glass. Twist a strip of orange zest over the top, drop it in, and serve.
This recipe is a classic although it seems no one is quite sure of its origins. Many recipes say to use Old Tom gin, which is a little sweeter than most gins.