Take out a fairly large trifle bowl – approximately 2.2 litre (3¼ pint) in capacity, or 24 x 18cm dish with 6cm side, or you could use 6-8 tall glasses
Make a syrup by placing half of the caster sugar in a saucepan with the water. Bring to the boil slowly on a medium heat for two minutes. Turn off the heat, leave to cool a little for 5 minutes.
Next add the the crème de cassis (or crème de framboise) and strawberries. Allow to cool completely.
Chop 150g of the chocolate into small pieces and melt in the microwave or a small bowl over a saucepan of simmering water. Remove from the heat and allow to cool a little.
In the meantime, beat the egg yolks with the remaining sugar in a large mixing bowl until thick and pale.
Beat in the mascarpone cheese until really smooth
Next stir in the cooled melted chocolate.
In a separate really clean bowl, whisk the egg whites until they form stiff peaks. Fold them into the mascarpone and egg mixture until well combined – be gentle.
Next strain the fruit mixture through a sieve set over a bowl to catch the draining syrup.
Dip half of the biscuits in the cooled syrup and use them to line the base of the serving dish or glasses.
Spread half of the mascarpone mixture over the biscuits, followed by half the fruit. Next cover the fruit with a second layer of the biscuits dipped in the liquid - then spread over the remaining fruit, followed by the remainder of the mascarpone mixture.
Grate the 30g of white chocolate left over from the ingredients over the top of the dish or glass of tiramisu.
Cover with cling film and chill in the fridge overnight if possible or for a minimum of 5 hours. This will allow the juices to be absorbed into the biscuits.