I am sorry to keep banging on about mousses. But their preparation raises a few issues that I have not yet resolved. Here is another recipe, following the one for cold caramel souffles, adapted from Margaret Costa's Four Seasons Cookery Book. Notes follow.
5 eggs -- 3 whole, and 2 separated
55g caster sugar
1 orange, zest and juice
1 lemon, zest and juice
4 leaves gelatine
150 ml double cream
In a bowl suspended over hot water, beat the eggs, egg yolks and sugar until they are pale and thick. Soak the gelatine leaves in cold water for about four minutes, until they are soft and slippery. Remove them from the water, and gently squeeze them. Put the orange juice and lemon juice in a pan on a gentle heat; when the liquid is warm, but long before it shows signs of bubbling, stir in the gelatine, which should dissolve. Beat this juice into the egg, and allow to cool.
When the egg and juice are starting to set, lightly whip the cream, and whip the egg whites until they form stiff peaks. Fold cream and egg whites into the egg mixture. Pour into glasses, cover with clingfilm, and put in the fridge to set.
I thought that I had an orange in the house; I did not. I grated a satsuma -- which, being soft, is not well suited to such a procedure. Then I squeezed the juice from it. The resulting mousse needed a little more citric tartness.
After misjudging the amount of gelatine I had needed for the caramel souffle, I poured the beaten egg and sugar into a measuring jug. They reached the 600 ml mark. I had yet to add cream and fruit juice. Each gelatine leaf, according to my packets, sets 200 ml liquid. Hence the four leaves.
At what point do you decide that the gelatinous egg and juice mixture is "starting to set"? I am not sure; but I think that I, nervous of trying to blend cream and egg white into jelly, tend to jump the gun. You want the juice to be thoroughly merged into the mousse. It separates from the egg mixture; but then it gets stirred in again, and the folded-in cream and egg white hold it in suspension. There was just a very thin layer of juicy jelly beneath my mousses; had the mixture been thicker, it might not have escaped.
What does "lightly whipped" mean? I whipped the cream until it held its shape, but before it would have gone stiff . But that appeared to be too much -- the cream stayed in globs in the egg mixture, and had to be beaten in to be properly incorporated. So I think that you should whip the cream until it just starts to thicken while remaining liquid, stir it into the gelatinous egg and juice, and then fold in the egg whites.