To make the filling (this is best pre-made the evening before to allow time to set), pour 500ml of ProZero into a medium size pan with the butter, sugar and vanilla paste. Heat gently until the butter has melted and the sugar dissolved.
In a small bowl mix the cornflour with the remaining 100ml of ProZero. Pour this into the pan and over a medium heat keep stirring until the mixture thickens (this will take a couple of mins).
Once you have a smooth thick sauce pour into a bowl, leave to cool. Then cover with cling film and place in the fridge to chill and set firm.
To make the tiramisu heat your oven to 180ºC/Gas4.
Grease and line the base of a 20cm loose bottom cake tin. Mix the Fate low protein cake mix and butter in a mixing bowl using an electric mix whisk until smooth.
Mix the coffee powder with the hot water and add to the cake mixture, beating for a minute until thoroughly combined.
Pour the mixture into the loose bottomed cake tin and bake for 20 mins.
Make up the boozy drizzle by mixing the strong coffee with the marsala and sugar.
Take the set cream filling from the fridge and beat with an electric whisk to lighten.
Take the cooled sponge and cut in half horizontally to create two discs.
Place one half into the base of a deep filled 20cm cake tin. Drizzle over some of the marsala and coffee mix to soak the sponge.
Pour half the filling onto the base and spread out until smooth and level. Top with the remaining sponge disc.
Soak the layer of sponge with the remaining boozy drizzle.
Spread the remaining creamy filling on top and dust with the mix of grated Vitabite bar, coffee and sugar.
Place in the fridge for at least 2 hours to set.
Cut small circles out of the sponge and place in small glass ramekin dishes to make several mini tiramisu.
Fate low protein cake mix, ProZero and Vitabite are foods for special medical purpose and must only be used under medical supervision. Always check the protein content on labels as ingredients on labels can change. Use the NSPKU foods list to check for permitted foods.