1. Sterilize the Jars and Lids: Boil jars and lids in water for 10 minutes to sterilize them.
2. Prepare the Brine: In a large pot, combine the white vinegar, water, sugar, salt, smashed garlic, mustard seeds, black peppercorns, dill seeds, and bay leaf. Bring the mixture to a boil, stirring until the sugar and salt are dissolved.
3. Prepare the Ingredients: Cut the kielbasa sausage into 1-inch pieces, peel the hard-boiled eggs, and thinly slice the onions.
4. Pack the Jars: Layer the kielbasa pieces, hard-boiled eggs, and sliced onions into sterilized jars, ensuring even distribution.
5. Add the Brine: Pour the hot brine over the packed ingredients, ensuring they are fully submerged. Leave about 1/2 inch of headspace at the top of each jar.
6. Seal the Jars: Wipe the rims of the jars clean and place the lids on. Screw on the bands until they are fingertip-tight.
7. Process the Jars: Process the jars in a boiling water bath for 10 minutes, ensuring they are fully submerged. Maintain a gentle boil throughout the process.
8. Cool and Store: Carefully remove the jars from the water bath and let them cool to room temperature. Check that the lids have sealed properly. Store the jars in a cool, dark place.
9. Allow Flavors to Develop: Allow the pickled kielbasa, eggs, and onions to sit for at least a week before consuming to let the flavors meld.
10. Conservation: Store unopened jars in a cool, dark place for up to several months. Once opened, refrigerate and consume within a few weeks. Ensure the ingredients remain submerged in the brine to prevent spoilage.