1 bunch spring onions (approximately 1/2 pound once trimmed and cleaned)
1/2 cup apple cider vinegar
1/4 cup water
3 tablespoons sugar
1 teaspoon sea salt
1 teaspoon mustard seeds
1/2 teaspoon celery seeds
1/8 teaspoon red chile flakes
Prepare a small boiling water bath canner and one pint jar.
Wash and thinly slice trimmed spring onions into thin rounds. In a small pot, combine vinegar, water, sugar, salt, mustard seeds, celery salt and red chile flakes. Bring to a boil. Once brine is simmering, add onions. Stir to combine and cook until onions are heated through, 2 to 3 minutes.
Remove pot from heat and funnel onions into prepared pint jar. Wipe rim, apply lid and ring, and process in a boiling water bath canner for 10 minutes. When time is up, remove jar from canner and let it cool. Check to ensure a good seal once jar is cool.
Let pickles rest at least 2 days before using. Unopened, this pickle will keep for up to one year in a cool, dark place. Once opened, keep refrigerated and use within 2-3 weeks.