I was introduced to chive blossom vinegar three years ago thanks to Marisa McClellan's blog, Food in Jars. My love for this vinegar necessitated the addition of chives to my garden, so I'd always have an adequate supply of blossoms for multiple batches. If you don't grow your own, pick up an extra bunch at the farmers market -- you'll want to have enough to make some for yourself, and some to give as gifts. You won't find a prettier host/hostess gift. —Lindsay-Jean Hard
Wine wine vinegar or other lightly colored vinegar, like distilled or champagne vinegar
Wash your chive blossoms and gently dry them. I use our no salad spinner necessary method: https://food52.com/blog/6202-how-to-wash-greens-without-a-salad-spinner.
Put your chive blossoms in a jar. Pick a container that you can fill at least halfway with blossoms -- I choose a jar that I can fill 2/3 to 3/4 full of blossoms.
Fill your jar with vinegar. You want to stick with a clear or lightly colored vinegar so you don't miss out on the delicate purple color the blossoms will impart. You can use either a single type of vinegar or a blend. I generally do a mix of part white wine vinegar and part distilled, but I'm also partial to a blend of mostly distilled vinegar with a small amount of ume plum vinegar.
Let your jar hang out in a cupboard (or other cool, dry place) for a week or two (stick to two weeks if your jar is only half full of blossoms), then strain the vinegar (discarding the blossoms), and transfer it to a new jar.