If you are in a pinch, you can use a dry white wine or another fortified wine as a sub for dry sherry. If you use a dry white wine, I would use Sauvignon Blanc or Pinot Grigio. Keep in mind, this will change the original flavor and you will have a white wine sauce for lobster ravioli. If you don't have a dry white wine, I suggest using a fortified wine, such as dry vermouth. Dry vermouth can be used as replacement for cooking sherry.