You’ll need a clean canning jar – the one shown here is a 3-cup ‘pint and a half’ jar. Pick a big handful of chives, and snip off just the flower heads. Soak those briefly in cold water, to eliminate any dust or critters, then remove from the water and gently dry.
Put the dry blossoms into your jar; it should be about three-quarters filled. Pour white distilled vinegar into the jar, filling it completely, and put on a lid.
Let it steep for a week or two in a cool dark place, then strain the flowers out, putting the now pink chive blossom vinegar into a fresh clean jar.
Keep the vinegar away from light in a cool place. Plan to use it up before autumn.