Place cornflour into a small jug or bowl.
Add 25ml ProZero and stir to make a smooth paste.
Pour the remaining ProZero, butter, Vitabite and sugar into a small saucepan and place over a gentle heat until simmering and the Vitabite has melted.
Add cornflour paste and stir constantly until the custard comes back to a simmer and has thickened.
ProZero and Vitabite are foods for special medical purposes and should be used under medical supervision.
This recipe has been specifically designed for a low protein diet. Refer to labels for allergen and other product information.