tablespoon pickling spices, tied in double layer of cheese cloth
Layer the eggs with the onion in a 2 quart jar to within 1" of the top. Put all the brine ingredients (except spice bag) in a pot and over medium heat bring to a boil, stirring until the sugar dissolves. Swish the spice bag around in the brine for 30 seconds.
Pour brine over the eggs, leave for 2 weeks in the fridge before serving.