Boil the eggs: Place eggs in a pot and cover with cold water by about an inch. Bring to a gentle boil, then lower to a simmer and cook 10–11 minutes for firm yolks. Avoid a rolling boil to prevent rubbery whites.

Chill and peel: Transfer eggs to an ice bath and chill at least 10 minutes. Crack and peel under cool running water. Pat dry. If shells are stubborn, roll the egg gently to loosen before peeling.

Make the brine: In a saucepan, combine vinegar, water, sugar, salt, onion, garlic, mustard seeds, peppercorns, coriander seeds (if using), bay leaves, and red pepper flakes. Bring to a simmer over medium heat, stirring until sugar and salt dissolve. Simmer 2–3 minutes to bloom the spices.

Cool slightly: Remove brine from heat and let it cool for 10–15 minutes. It should be hot but not boiling when poured over the eggs to avoid toughening the whites.

Pack the jar: Place peeled eggs in a clean, heat-safe quart jar or container. Tuck in onion slices and optional extras like dill or jalapeño. Make sure the jar is large enough to fully submerge the eggs in brine.

Pour and submerge: Pour the warm brine over the eggs until fully covered. If needed, top up with a bit more vinegar and water at a 2:1 ratio. Weigh eggs down with a clean, non-reactive weight or a small zip-top bag filled with brine if they float.

Chill and wait: Seal the jar and refrigerate. For the best flavor, wait at least 3 days before eating. They’re at their peak around day 5–7.

Serve: Enjoy halved with a sprinkle of salt and pepper, a dash of hot sauce, or a smear of mustard. They pair perfectly with cold beer, sharp cheddar, and pickles.