There are all sorts of recipes around for tarragon vinegar using different kinds of vinegar (white, white wine, cider, red) . I ended up using tarragon, garlic, red pepper flakes and white wine vinegar.
Garlic, Tarragon from my herb garden, dried red pepper (my own peppers, dehydrated and ground).
Filled with white wine vinegar
I cut several long stalks of tarragon and broke them into pieces. Peeled 2 cloves of garlic and added a liberal sprinkling of crushed, dried red pepper. Put in the jar (that's been cleaned and dried) and fill to top with white wine vinegar. I'll put the jar in the basement to sit and steep for several weeks, then decant into a new jar.