I'm confused about when and where to add some of the egg whites in the Pistachio Souffles recipe in How to Be a Domestic Goddess. The recipe says to fold the 5 whisked egg whites into the pistachio mixture, a quarter at first and then the rest. But how about the other 4 egg whites from the separated eggs? Do those get added at some point? Where? Thanks...
Nigella's Pistachio Souffles recipe (from [HOW TO BE A DOMESTIC GODDESS](/books/how-to-be-a-domestic goddess)) uses the yolks from 4 eggs to enrich a thick, pistachio-flavoured custard. Egg whites are then whisked and incorporated into the custard and when this mixture is baked the air trapped in the whites expands, causing the souffle to rise.
The recipe says 5 egg whites and this should be made up of the 4 egg whites from the separated eggs plus one extra egg white. Adding one extra egg white to the whites from separated eggs helps to add extra lightness and lift to the souffle. If you ever have egg whites left over from another dish it is useful to freeze them in a small bags or airtight containers so that you can defrost them and use them up in a recipe like the Pistachio Souffles.