Step 1: Preheat the oven to 160°C (325°F) and grease a 22 cm diameter detachable springform pan.
Step 2: Mash biscuits to fine crumbs. Mix them with the melted butter and press the mixture firmly into the bottom of the mold. Bake for 10 minutes and then let cool completely.
Step 3: In a large bowl, beat the cream cheese with the sugar until creamy and smooth. Add the eggs one by one, mixing well after each addition until just combined.
Step 4: Add the whipping cream, vanilla essence, and lemon zest (if using). Mix on low speed until just combined, being careful not to over-beat the mixture.
Step 5: Pour the cream cheese mixture over the cooled biscuit base in the springform pan and gently smooth the surface with a spatula.
Step 6: Place the springform pan into a larger roasting tray. Carefully pour hot water into the roasting tray, reaching about halfway up the sides of the cheesecake pan (this is called a water bath or bain-marie). Bake for 50-60 minutes, or until the edges are firm but the center still has a slight wobble.
Step 7: Turn off the oven, leave the door slightly ajar, and let the cheesecake cool inside the oven for 1 hour. This slow cooling helps prevent cracks.
Step 8: Remove the cheesecake from the oven and the water bath. Let it cool completely on a wire rack at room temperature. Once cooled, refrigerate for at least 4 hours, or preferably overnight, to allow it to set fully.
Step 9: Before serving, gently remove the cheesecake from the pan. Garnish with fresh blueberries and sprinkle generously with powdered sugar.