Line the bottom of a round springform cake tin (20cm) with baking paper.
Crumble the Tim Tams in a food processor and add this to the cake tin. Press down well using a spoon or ladle to form a tight base. Refrigerate.
Add the milk, condensed milk and salt to a pot; bring to boil and then simmer gently till you get the consistency of a thin custard. Make sure you keep a close eye stirring often or else the mixture can bubble over. Remove from heat and allow to cool down completely and then refrigerate for at least 30 minutes.
Beat the chilled cream to get soft peaks. Add the vanilla essence and then gently fold in the chilled condensed milk mixture till combined well.
Pour this over the Tim Tam mixture in the baking tin and freeze for at least 4 hours or till completely set. Remove from the cake tin onto a serving stand.
To decorate, I lined the edges of the icecream cake with chocolate shavings. Added 2 Tim Tams to the top and a handful of sprinkles. Just let your creative juice flowing and decorate it however you wish to.