Melt the Vitabite in a heatproof bowl over a pan of boiling water and set aside to cool.
Beat the butter in a large bowl until soft. Add the icing sugar and beat until smooth.
Fold the cooled, melted Vitabite into the butter and icing sugar mixture until combined.
If the mixture is too thick, stir in a small amount of ProZero.
Spread on top of a low protein cake or cupcake!
ProZero and Vitabite are foods for special medical purposes and must be used under medical supervision.