Chill a martini glass. Fill a martini pitcher with ice. Add the gin, and the vermouth and stir for no more than 30 seconds. Pour into the chilled glass. Garnish with a cocktail onion.
Variation: to make a traditional Martini use 3 parts gin and 1 part dry vermouth. To make a Perfect Martini use ¼ oz dry vermouth, ¼ oz sweet red vermouth and 1 ¼ gin. To make a Sweet Martini use 1 ½ oz gin, ½ oz sweet vermouth and garnish with a cherry. To make Vodka Martini use 1 ½ oz vodka, ½ oz dry vermouth and garnish with olive. To make a Martini Dry use 5 parts gin, 1 part dry vermouth and garnish with a cocktail onion, olives, or a twist.