This is a very fine eighteenth-century recipe because it sets perfectly without the use of gelatine, which so many recipes for a fruit mousse require. If gelatine is used the mousse is much more likely to separate so that there is a layer of jelly at the bottom.
Separate the yolks and whites of the eggs and beat the yolks thoroughly. Grate the yellow part of 4 rinds finely, then squeeze the juice from all the fruit. Heat the juice, grated rind and sugar together, stirring until the sugar is dissolved. Allow to cool. Now pour the mixture on to the egg yolks, beat well and stir over a saucepan of boiling water till the mixture thickens. Allow to cool to blood heat. Meanwhile, beat the egg whites until they will hold a peak when dropped from the whisk. Add the orange mixture to the egg whites slowly, and fold in, disturbing the whites as little as possible, but making sure that the whites and the orange are mixed right through. Pour the mixture into the serving dish and place in the refrigerator for several hours, stirring two or three times during the first hour.
©1975 The Estate of Elizabeth Ayrton