Preheat the oven to 160°C and line a 9 inch loose bottom square baking tin with parchment paper
Blitz 200g of custard creams in a food processor until a fine crumb then add to a bowl and mix with the melted butter
Pour the biscuit mixture into the base of the loose bottom tin and pack it down tightly with the pack of a spoon into all the corners.
Bake the base in the oven for 8-10 minutes then remove and leave it aside to cool slightly.
To make the filling, combine the cream cheese and sugar until smooth then add the sour cream, eggs, egg yolk and custard powder and blend until smooth.
In a separate bowl crush the fresh raspberries into a pulp, then add the icing suagr and lemon juice and mix until combined.
Push the raspberry mixture through a sieve to separate the raspberry seeds. This is your raspberry couli.
To assemble the cheesecake, pour the cheesecake mixture on top of the custard cream base then spoon dots of raspberry coulis randomly over it. Swirl the raspberry coulis into the cheesecake batter with a knife to create a ripple effect.
Top with the remaining 50g custard cream biscuits then put the baking tin into a roasting dish and place it into the oven on the centre shelf.
Pour boiling water into the roasting dish to create a water bath for the cheesecake to bake in. You want to ensure the baking tin is covered about 50% in water.
Cover with tin foil to stop the custard creams from burning and bake for 40-45 minutes then once baked turn the oven off and leave the door ajar and allow the cheesecake to cool.
Once the oven is cool remove the cheesecake from the oven and let it cool completly before removing it from the tin. MY KITCHEN TIP : For a perfect cut you could leave in the fridge overnight and then slice it the next day.