Here's my recipe. This will make a little over 1 cup of sauce. Enough for more than a few oysters.
1/2 cup champagne
1/2 cup champagne vinegar
2 finely chopped shallots
1 T of minced celery leaves
1 1/2 t sea salt
4 t of freshly cracked black pepper
Mix all ingredients well. Serve at room temperature.