Certain recipes (such as macarons, for instance,) call for 'aged egg whites'. Simple enough, although it does require planning in advance as the egg whites must be separated around two days before they are needed for the recipe (adventure) in question.
- Crack your egg on the side of a bowl and juggle the yolk backwards and forwards between the two shells. Let the white trickle into an immaculately clean bowl 'A'. Be careful not to let the whites dribble around your fingers as natural oils from your skin may ruin the 'whippability' of the whites. Save the yolk for another recipe and bin the shells.
- Transfer the contents of bowl 'A' to bowl 'B'. This way, should an egg yolk burst into the first bowl, it will not ruin the previously divided egg whites as these will be sitting in bowl 'B'.
- Repeat this process for each egg whilst following the 'if in doubt, throw it out' rule. Any trace of egg yolk (fat) will ruin your meringue.
- Cover bowl 'B' with plastic wrap and poke some holes into it so as to help with the evaporation process.
- Refrigerate for 1-4 days and then use as required.