I am making the Salted Caramel Sauce. I can't purchase fleur de sel locally so I picked up Mediterranean Sea salt. Is this an acceptable substitute and are the quantities the same or need to be adjusted? If adjustment is necessary; by what ratio?
Nigella's Salted Caramel Sauce is an easy to make version of this sauce, which Nigella flavours with fleur de sel. Fleur de sel is harvested from evaporated sea water and tends to come in crystals that are larger than table salt. Mediterranean Sea salt is also harvested from sea water but often comes in finer, more free-flowing grains that are more similar in size to table salt. So any adjustment may depend on the size of the salt crystals that you have purchased. By volume one teaspoon of fleur de sel crystals is approximately equivalent to half a teaspoon of fine salt.
However for Nigella's Salted Caramel Sauce the amount of salt added can very much be adjusted to personal taste. So we would suggest using a quarter of a teaspoon of salt to start with and then very carefully tasting the sauce (it will be hot so take a little on a teaspoon and let it cool before tasting) and adding more salt, a pinch at a time, until the salt level suits your own taste.