Add 2 oz rye whiskey (or bourbon) to a mixing glass with ice
Add 1 oz sweet vermouth
Add 2 dashes Angostura bitters
Stir until very cold (about 30–45 seconds)
Strain into a chilled coupe or rocks glass over fresh ice (or without ice for a coupe)
Garnish with a maraschino cherry or an expressed lemon peel
Serve immediately