Combine caramel ingredients in a saucepan and bring to boil, stirring continuously. Reduce heat to a light simmer and continue to stir for about 3-5 minutes (caramel with thicken up). You know it's done when you wipe your finger across the back of a spoon and it makes a line without dripping down.
In a bowl combine your puffed rice, whey protein powder and chopped peanuts. Pour caramel into the bowl while stirring. Ensure rice is evenly coated. Add a splash of milk if it's too dry.
Press rice crispy treat mixture into a brownie tray lined with baking paper. Compact well. Put into freezer.
Optional: melt chocolate and pour over as a topping.