Put the cream, lemon zest and sugar into a large bowl
and whisk them together until the mixture starts to
thicken. Add the lemon juice and whisk again until the
mixture thickens further, don’t let it get too stiff or you
won’t be able fold in the egg whites.
Whisk the egg
whites until they form soft peaks and then fold them
into the lemon mixture. Spoon the mousse into 4 glasses
and chill. Decorate with extra zest if you like.