Caramel Filling
1. Place chopped butter, brown sugar and condensed milk in a heavy-based, non-stick saucepan over medium-low heat.
2. Cook, stirring constantly with a wooden spoon (as mixture can stick to pan), for 10-12 minutes, or until mixture thickens and becomes golden (or cream-coloured).
3. When the thick caramel mixture comes off the sides of the saucepan, then it’s ready.
4. Pour the hot caramel over the roasted nuts. (Be careful! Hot caramel can sear the skin off!)
5. Using the back of a spoon, smooth the surface of the caramel until layer is flat.
6. Refrigerate for 15 minutes.