In a mixing glass, combine the gin, sweet vermouth, maraschino liqueur, and Angostura bitters.

Fill the mixing glass with ice, ensuring there's enough to chill the mixture without diluting it too much.

Strain the chilled cocktail into a coupe glass that has been pre-chilled in the freezer for a smoother experience.

Express an orange twist over the drink to release its oils, and then drop it into the glass as a garnish.