Preparation Bring vinegar, sugar, salt, peppercorns, mustard seeds, and 2 cups water to a boil in a medium pot over high heat, stirring occasionally. Reduce heat to medium-low and simmer 10 minutes. Place carrots in a heatproof resealable container or jar (divide among several containers if necessary). Pour hot brining liquid over carrots. Let cool to room temperature, then cover and chill at least 2 hours before serving. Cooks' NotePickles can be chilled in a resealable container for up to 3 weeks.