Step 1
Prepare all the ingredients.
Step 2
In a large pot, place the eggs and cover them with cold water. Bring the water to a boil, then remove from the heat. Cover the pot and let the eggs sit in the hot water for 10 to 12 minutes.
Step 3
Transfer the eggs to a strainer and rinse them under cold water for 1 minute. Return the eggs to the pot, fill it with cold water, and let them cool enough to handle, which takes about 2 to 3 minutes. Peel the eggs and place them in a 1-liter wide-mouth jar.
Step 4
In a saucepan, combine the vinegar, water, most of the sliced onion, salt, pickling spice, and peppercorns. Bring the mixture to a rolling boil.
Step 5
Pour the mixture over the eggs in the jar. Place the remaining onion slices on top and seal the jar. Let it cool to room temperature, which takes about 1 hour, then refrigerate for 3 days before serving.