In a sauté pan, simmer the onion and tarragon in the chicken broth.
When the onion is tender, add the mustard and honey.
You might need a bit more broth or you can enhance it with some cream to make it more elegant.
Much of the hot-house grown tarragon really doesn't have much flavor. If you are thinking of going for fresh, smell it to tell if it is going to taste good. Dried tarragon is typically flavorful if it's not old. All old dried herbs taste like sawdust. Dried tarragon is stronger than fresh.