Tip the egg whites into a clean bowl and, using a handheld electric whisk, whisk to soft peaks. Add the remaining 175g of caster sugar a little at a time, whisking between each addition, until you have a lovely, glossy meringue that holds soft peaks. Spoon the meringue over the top of the jam, using the spoon to make little peaks – like the peaks of the queen’s crown – or you can put the meringue into a piping bag and pipe it over the top.
