To make any herb or flower vinegar, all that is required is some good quality vinegar suited to the intended infusion, a jar, and the herb. For chive blossoms, we want to see the color and taste the fresh garlicky flavor, so we choose a white wine or rice vinegar. For this batch, it was white wine vinegar.
Within a few days, the color transfers from the flowers to the vinegar. For flavor, you'll want to taste the vinegar after about a week, and then decide whether to let it continue steeping or not. This vinegar was the right flavor for me in about 10 days. Some vinegars you can just allow to sit until you're ready to use them - entirely up to you!
After it was strained, I picked a few fresh blossoms and put them into the bottles I'd be using. The color will stay on the fresh blossoms, since the vinegar is saturated with color now.
The finished vinegar must be stored out of sunlight to retain the jewel toned brilliant pink color. Visions of luscious salads dressed with this vinegar and a little oil dance in my head.