Place the crackers on a lined baking sheet, set aside.
Place the butter and brown sugar into a saucepan and bring to the boil. Allow the mixture to simmer for 3 minutes until thickened, then pour over the crackers. Place into the oven at 350F for 15 minutes to crystallize.
Combine the chocolate chips in a bowl and microwave for 20 second bursts until fully melted. Pour on top of the toffee layer, then add the sprinkles and decorations.
Allow the Christmas crack to set in the fridge before breaking into smaller pieces.