Please note that you will have some pretzels, Jaffas and silver cachous leftover after decorating (perfect for nibbling on as you go!!).
You can buy silver cachous (small edible balls) in the baking section of most large supermarkets.
If you can't find Jaffas, you can use any red coated chocolate balls (or even red M&Ms).
The chocolate brownie can be prepared ahead of time and frozen in an airtight container until needed. Allow to come to room temperature before cutting and decorating.