Heat sugar, butter and ProZero in a pan over a medium heat. Bring to the boil and stir well.
Add the marshmallows, free from white chocolate buttons and vanilla essence and take off the heat. Stir until melted.
Separate the mixture into 3 bowls and add 1 tsp of each different food colouring to each bowl.
Layer the 3 colours in a baking tray lined with cling film and swirl through them with a knife to create a rippled appearance.
Cover with permitted sprinkles or toppings of your choice.
Set in the fridge for 4 hours or until hard.
ProZero is a food for special medical purposes and must be used under medical supervision.