Line a 9-inch springform pan with baking paper. Crush the digestive biscuits until fine crumbs form, then mix with melted unsalted butter until well combined. Press into the bottom of the pan and chill for at least 30 minutes.

Preheat the oven to 140°C (285°F). In a mixing bowl, beat the cream cheese and sour cream until fluffy. Gradually add the caster sugar and passion fruit pulp. Add eggs one at a time, mixing gently.

Pour the cheesecake batter over the chilled biscuit crust. Tap gently to release air bubbles. Bake for 60-70 minutes, until edges are set but center jiggles slightly.

After baking, turn off the oven and open the door slightly to allow the cheesecake to cool for about an hour. Then cool at room temperature for another hour and refrigerate for at least 3 hours, ideally overnight.

In a saucepan over medium heat, combine passion fruit pulp, sugar, cornstarch, and lemon juice. Stir until thickened (5-7 minutes). Let it cool before pouring over the cheesecake.

Remove springform pan sides and slice the cheesecake. Garnish with fresh passion fruit slices, mint leaves, or desiccated coconut before serving.