Crust: In a medium bowl combine biscuit crumbs, sugar and butter. Mix well and press into the bottom of a 21cm springform tin.
Filling: In a large bowl beat cream cheese and sugar until smooth. Beat in almond essence and salt. Blend in the eggs one at a time, on low speed. Stir in 3 tablespoons amaretto liqueur. Pour filling into crust.
Bake in the preheated oven for 40 to 45 minutes or until golden brown and filling is set. Allow to cool completely.
Topping: In a small bowl combine sour cream, 1 tablespoon sugar, 1/2 teaspoon almond essence and 1 tablespoon amaretto liqueur. Mix well and spread over top of cooled cake. Refrigerate 4 to 6 hours before removing from tin.