Boil the water and Chelsea White Sugar together for about 20 minutes, stirring only until the sugar has dissolved. Mix the cornflour with the grape juice and add it gradually to the syrup, stirring constantly. Boil until very thick.
Remove the pan from the heat and add the rose water, nuts and food colouring. Pour the mixture into a shallow well-greased tray and let cool.
When set, cut into squares with a sharp knife. Roll the pieces in Chelsea Icing Sugar to coat.
Grease and line a 16cm x 26cm slice pan with baking paper, allowing the 2 long sides to overhang. Place the white chocolate in a heatproof bowl over a saucepan of gently simmering water (make sure the bowl doesn’t touch the water). Melt the chocolate, stirring occasionally, until smooth.
Combine the Turkish delight, biscuits, pistachios and marshmallows in a bowl. Pour over melted chocolate and stir to combine. Spoon into prepared pan. Place in the fridge for 2 hours or until set. Cut into rectangles and package up with cellophane and ribbon to make Christmas crackers.
TIP: Package up any leftover Turkish delight and gift separately.