• Cut a circle of parchment paper to line the bottom of your springform cake tin. If you butter the bottom of the pan first, the baking paper will stick to it.
• Double-wrap the cheesecake pan in large sheets of aluminum foil all the way up the sides of the springform pan. This will prevent the water from seeping into the cheesecake when we bake it in a water bath.
• Preheat the oven to 160°C Fan.

Make Biscuit Crust

• Place your butter in a small saucepan and set it over low heat until it melts.
• Place the biscuits into a food processor and blitz them into fine crumbs. If you don’t have a food processor, you can place the biscuits in a sturdy ziplock bag and bash them with a rolling pin. Or place the biscuits into a high-rimmed metal mixing bowl, and use the flat end of a rolling pin to crush them thoroughly.
• ​Pour the melted butter over the crumbs and mix well.
• Spoon the mixture into the prepared pan and press it down into the base using the pack of a spoon, or a blast bottom of a glass. You should have an even layer of biscuit mixture.
• Place the cake tin in the preheated oven for 10 minutes.
• Take the tin out and leave the cheesecake crust to cool down.
• Reduce the oven temperature to 140°C Fan.

Make Cheesecake Filling

• Place the cream cheese, creme fraiche, and caster sugar into a large mixing bowl. Using an electric hand mixer, beat the mixture for approximately 2 minutes on high speed, scraping the sides midways through.
• Pour in the fresh lemon juice and beat again just enough to combine.
• ​One by one, add the eggs, mixing them in using a balloon whisk (don’t use an electric mixer, as it will pump in too much air into the cheesecake batter and your cheesecake may crack). Mix in the egg yolk.
• Finally, drain the thawed blueberries and add them to the cheesecake mixture alongside the lemon zest, and mix everything gently to distribute.

Bake and Cool Cheesecake

• Pour the lemon and blueberry cheesecake mixture on top of the biscuit base. Smooth out the top of the cheesecake filling using an offset spatula. Set the cheesecake into a high-rimmed roasting pan, pour hot water about halfway up the cheesecake pan, and place it in the centre of the oven for 1 hour (note, baking time is given for a 7 in (18cm) baking pan).
• After an hour, turn the oven off, but don’t open the oven door. Leave the cheesecake to finish cooking in the closed oven for another hour. Then open the oven door a crack and leave it to cool gradually for another hour.
• Take the cheesecake out of the oven, out of the water bath and out of its foil wrap, and leave it to cool down to room temperature. Finally place it in the fridge for at least 4 hours, or ideally, overnight.

Make Blueberry Sauce

• Place the blueberries (they don’t need to be thawed for the sauce), water and sugar in a medium saucepan. Set it over low heat until blueberries defrost, sugar dissolves and the mixture starts gently bubbling around the edges. Let the blueberry mixture bubble for 5 minutes over medium heat.
• Mix cornflour (cornstarch) with 1 tablespoon of cold water in a small bowl. Pour the cornflour slurry into the blueberries and mix. You may need to return the sauce to the stovetop and stir for a few minutes for the blueberry sauce to thicken, but note that it will thicken further as it cools.
• Leave the sauce to cool down to room temperature, then store it in the fridge covered with a piece of plastic wrap until you are ready to serve.
• Take the chilled cheesecake out of the tin and slice into portions. Serve your cheesecake with the blueberry topping. Garnish each slice with extra lemon zest and a sprig of mint, if you wish.