Make base: Process biscuits to fine crumbs. Transfer to a large bowl; stir in almonds, nutmeg and butter. Press the crumb mixture firmly over the base of a 22cm non-stick springform tin. Refrigerate while preparing the filling.
Make filling: Combine sugar and water in a medium saucepan; stir over medium heat until sugar is dissolved. Bring to the boil, then boil, uncovered, without stirring, for about 10 minutes or until the syrup is a rich golden colour.
Remove from the heat and immediately add 250 grams of the cream cheese. Be careful, as this will cause the mixture to froth up. Whisk continually until the cheese is combined with the caramel.
Place the caramel mixture in medium bowl of an electric mixer with the remaining cream cheese; beat until well combined. Add the eggs and vanilla, beating well between additions.
Pour the filling into the base; place tin on an oven tray. Bake for 25 minutes. Remove from the oven. Increase the oven temperature to 200°C (180°C fan-forced).
Make topping: Combine sour cream, sugar and vanilla in a bowl; spread evenly over cheesecake. Bake for a further 10 minutes.
Cool cheesecake then refrigerate for 6 hours before serving. Dust with sifted icing sugar, if desired.
If you don't have six hours, chill the cheesecake for half an hour in the freezer before refrigerating.