Mix together the biscuit crumbs and
melted butter or margarine and press into the base and sides of a
greased 20 cm/8 in loose-bottomed cake tin (pan). Chill.
Sprinkle the gelatine over the water in a bowl and leave until spongy.
Stand the bowl in a pan of hot water and leave until dissolved. Leave
to cool slightly. Peel and stone (pit) the avocados and mash the flesh
with the lemon juice and rind. Beat in the cheese and sugar. Stir in
the dissolved gelatine. Whisk the egg whites until stiff, then fold
them into the mixture using a metal spoon. Whip half the cream until
stiff, then fold it into the mixture. Spoon over the biscuit base and
chill until set.
Whip the remaining cream until stiff, then pipe it decoratively on top
of the cheesecake.