1 tsp. whole black peppercorns 1/8 tsp. freshly grated nutmeg 3 sprigs thyme 2 cups dry vermouth 1 cup white wine vinegar ½ cup sugar 1 tbsp. kosher salt 10 oz. white pearl onions, peeled
Place peppercorns, nutmeg, and thyme in a 1-qt. sterilized glass jar; set aside. Bring vermouth, vinegar, sugar, salt, and ½ cup water to a boil in a 2-qt. saucepan over high heat, stirring until sugar and salt dissolve; add onions, and cook for 1 minute. Transfer onions and brine to jar and seal with lid; let cool to room temperature. Refrigerate at least 4 hours before using.