Grease a slice or lamington tin. Place all the biscuits from a packet of Tim Tams in a plastic bag and crunch up with rolling pin. Spread the crushed biscuits on the base of the tray.
Melt the butter in a medium saucepan on medium heat, then add the brown sugar and ice-cream, simmer for 2 minutes. Pour this mixture over the crushed biscuit and refrigerate until firm.
Melt the chocolate in the microwave or in a double boiler until runny, make sure you don’t burn it. Pour this over the refrigerated caramel and biscuit and spread evenly. Put in the refrigerator until chocolate has set.