Start by making the jam. Cook together the frozen strawberries, 3 tbsp caster sugar and lemon zest for 10-15 minutes. When ready, blitz together to form a chunky jam and cool down. Next, soak the biscuits in the soaking syrup and lay side by side in a ceramic or glass rectangular dish. Pour over the prepared strawberry jam. For the cream whip together the double cream, 2 tsp vanilla and 3 tbsp icing sugar till firm. Add in the cream cheese and continue to whisk till smooth. Spoon this mixture over the strawberry jam and level out. Place into the fridge and chill for 1 hour to set. Heat the pistachio cream slightly to make runny and pour all over the top of the cream and cover completely with the chopped pistachios. Chill for another hour before serving.