Place almonds in food processor and pulse until coarsely chopped. Add vanilla wafers and process until fine. Blend in butter until crumbs are moistened and remove.
Press mixture into bottom and partly up sides of 10" springform pan and refrigerate.
Place 1/4 cup water in a medium sized, heavy saucepan. Sprinkle with gelatin and let stand for 5 minutes.
Rinse and dry work bowl and steel knife. Add egg yolks and 1 cup sugar. Process until light in colour. Add milk through feed tube and blend.
Dissolve gelatin over low heat and stir in milk mixture. Cook over low heat until custard begins to thicken. Cool for about 5 minutes.
Cut cream cheese into cubes and add to work bowl. Add almond extract and liqueur and blend. slowly add custard, blend and scrape down sides of bowl.
Arrange a mixing bowl nested in a larger bowl lined with ice cubes. Pour mixture into nested bowl. Stir occasionally to prevent setting around the outside edges. Cool unti mixture is thick and syrupy.
Beat eggwhites with 1/4 cup sugar until stiff. Whip cream until light and fluffy. To lighten the custard, stir 1/3 of the beaten egg whites into it first, then fold in remaining egg whites and 2/3 of the whipping cream. Turn mixture into prepared crust and refrigerate.
To the remaining cream, add icing sugar and liqueur. Whip until stiff. Pipe or spoon cream attractively over cake. Sprinkle the top with sliced toasted almonds and refrigerate the cake for 2-3 hours before serving.
This cake can be prepared a day ahead of serving time and can also be frozen.