Preheat oven to 180 C / Gas 4. In a medium bowl, combine digestive biscuit crumbs, butter and 3 tablespoons sugar. Mix well and press into the bottom of a 23cm loose bottomed cake tin.
In a large bowl, beat cream cheese and 100g sugar until smooth. Beat in almond extract and salt. Blend in the eggs, one at a time, on low speed. Stir in 3 tablespoons amaretto liqueur. Pour mixture over biscuit base.
Bake in the preheated oven for 40 to 45 minutes, or until golden brown and filling is set. Allow to cool completely.
Make the topping: In a small bowl, combine soured cream, 1 tablespoon sugar, 1 teaspoon almond extract and 1 tablespoon amaretto liqueur. Mix well and spread over top of cooled cheesecake. Refrigerate 4 to 6 hours before removing from tin.