Step 1. Preheat the Oven and Prepare the Pan

Preheat your oven to 325°F (160°C). Grease a 9-inch springform pan and line the bottom with parchment paper.

Step 2. Make the Biscuit Base

In a food processor, pulse the digestive biscuits until they turn into fine crumbs. Alternatively, place them in a ziplock bag and crush with a rolling pin. In a mixing bowl, combine the biscuit crumbs with the melted butter until well-coated. Press the mixture firmly into the bottom of the springform pan to create an even layer. Chill in the fridge while you prepare the filling.

Step 3. Prepare the Cheesecake Filling

In a large mixing bowl, beat the cream cheese and caster sugar together until smooth and creamy. Add the plain flour and mix until combined. Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract, sour cream, and lemon zest if using, and mix until the filling is smooth and lump-free.

Step 4. Pour the Filling into the Pan

Remove the springform pan from the fridge and pour the cheesecake filling over the chilled biscuit base. Use a spatula to smooth the top.

Step 5. Bake the Cheesecake

Place the cheesecake in the preheated oven and bake for 50-60 minutes, or until the edges are set but the center still has a slight wobble. Turn off the oven and leave the cheesecake inside with the door slightly open for 1 hour to cool gradually.

Step 6. Chill the Cheesecake

After cooling in the oven, remove the cheesecake from the oven and allow it to cool completely at room temperature. Then, refrigerate for at least 4 hours or overnight to set.

Step 7. Serve and Add Toppings

Remove the cheesecake from the springform pan and transfer it to a serving plate. Top with fresh berries, a dusting of powdered sugar, or a drizzle of caramel or chocolate sauce if desired.