Metaxa is a Greek brandy, good chance you won't have it in your drinks cabinet and it's no problem to use another brandy. I have been using Spanish brandy the last few times I made this, but the Metaxa does have a different flavor. If I make this for the two of us I do cut down on the chicken but make the same amount of sauce and serve it with pasta. It is a rich sauce with a distinct flavor. If you should use tarragon as an herb, taste the herb first it can be very strong sometimes and you should use less.